Standalone sulfide based lithium ion-conducting glass solid electrolyte and associated structures, cells and methods

ABSTRACT

A standalone lithium ion-conductive solid electrolyte including a freestanding inorganic vitreous sheet of sulfide-based lithium ion conducting glass is capable of high performance in a lithium metal battery by providing a high degree of lithium ion conductivity while being highly resistant to the initiation and/or propagation of lithium dendrites. Such an electrolyte is also itself manufacturable, and readily adaptable for battery cell and cell component manufacture, in a cost-effective, scalable manner.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication 62/086,641, filed Dec. 2, 2014, titled LITHIUM IONCONDUCTING GLASS LAYERS AND ASSOCIATED PROTECTED LITHIUM METALELECTRODES AND BATTERY CELLS; and from U.S. Provisional PatentApplication 62/111,048, filed Feb. 2, 2015, titled LITHIUM IONCONDUCTING GLASS LAYERS AND ASSOCIATED PROTECTED LITHIUM METALELECTRODES AND BATTERY CELLS; and from U.S. Provisional PatentApplication 62/146,809, filed Apr. 13, 2015, titled FREESTANDING LITHIUMION CONDUCTING ARTICLES AND ASSOCIATED ELECTRODE ASSEMBLIES AND BATTERYCELLS, and from U.S. Provisional Patent Application 62/149,250, filedApr. 17, 2015, titled FREESTANDING LITHIUM ION CONDUCTING ARTICLES ANDASSOCIATED ELECTRODE ASSEMBLIES AND BATTERY CELLS; and from U.S.Provisional Patent Application 62/165,791, filed May 22, 2015, titledLITHIUM ION CONDUCTING WALL STRUCTURES AND LITHIUM ELECTRODE ASSEMBLIESAND ASSOCIATED CONTINUOUS ROLLS AND LITHIUM BATTERY CELLS AND METHODS OFMAKING THEREOF; and from U.S. Provisional Patent Application 62/171,561,filed Jun. 5, 2015, titled STANDALONE INORGANIC SOLID ELECTROLYTESHEETS, AND STANDALONE LITHIUM ION CONDUCTIVE SOLID ELECTROLYTESEPARATORS, CONTINUOUS INORGANIC SEPARATOR ROLLS, LITHIUM ELECTRODEASSEMBLIES, AND BATTERY CELLS THEREOF, AS WELL AS METHODS OF MAKINGTHEREOF; and from U.S. Provisional Patent Application 62/196,247, filedJul. 23, 2015, titled STANDALONE INORGANIC SOLID ELECTROLYTE SHEETS, ANDSTANDALONE LITHIUM ION CONDUCTIVE SOLID ELECTROLYTE SEPARATORS,CONTINUOUS INORGANIC SEPARATOR ROLLS, LITHIUM ELECTRODE ASSEMBLIES,BATTERY CELLS THEREOF, AND METHODS OF MAKING; and from U.S. ProvisionalPatent Application 62/222,408, filed Sep. 23, 2015, titled VITREOUSSOLID ELECTROLYTE SHEETS OF Li ION CONDUCTING SULFUR BASED GLASS ANDASSOCIATED STRUCTURES, CELLS AND METHODS. Each of these applications isincorporated herein by reference in its entirety and for all purposes.

STATEMENT OF GOVERNMENT SUPPORT

This invention was made with Government support under Award No.:DE-AR0000349 and/or DE-AR0000772 awarded by the Advanced ResearchProjects Agency-Energy (ARPA-E), U.S. Department of Energy. TheGovernment has certain rights in this invention.

FIELD OF THIS DISCLOSURE

This disclosure relates generally to the field of lithiumelectrochemical devices and components thereof, and in particular tolithium battery cells, lithium electrode assemblies, and Liion-conducting solid electrolyte components (e.g., separators and solidelectrolyte sheets) for use in lithium battery cells, as well as methodsfor making said components, electrode assemblies and battery cells.

BACKGROUND OF THIS DISCLOSURE

There is a continuing need for high performance battery cells and theirassociated cell components, and particularly for high energy densitysecondary batteries.

SUMMARY

Provided herein is a standalone lithium ion-conductive solidelectrolyte, methods of making and using the electrolyte, and batterycells and cell components incorporating the electrolyte. An electrolytein accordance with this disclosure is capable of high performance in alithium metal battery by providing a high degree of lithium ionconductivity while being highly resistant to the initiation and/orpropagation of lithium dendrites. In addition, such an electrolyte isalso itself manufacturable, and readily adaptable for battery cell andcell component manufacture, in a cost-effective, scalable manner.

In one aspect, provided is a standalone lithium ion-conductive solidelectrolyte including a freestanding inorganic vitreous sheet ofsulfide-based lithium ion conducting glass. The glass has a liquid-likesurface, an area of at least 10 cm², a thickness of no more than 100 μm,and a room temperature intrinsic lithium ion conductivity of at least10⁻⁵ S/cm. The liquid-like surface lacks flaws sufficient to initiatelithium dendrite penetration. For example, the liquid-like surface lackssurface flaws having a depth dimension greater than 1% of the sheetthickness, preferably less than 0.1% of the sheet thickness, andgenerally no more than 5 μm. Such a surface can be obtained through meltprocessing of a sulfide-based lithium ion conducting glass, such as bydrawing molten glass or pulling/drawing a glass preform into a sheet. Asheet formed in this manner lacks powder particle, inter-particleboundaries, or contiguous void manifestations of a pressed powdercompact extending between first and second principal surfaces that aresufficient to propagate a Li dendrite, and the liquid-like surface lacksflaw manifestations of a pressed powder compact that are sufficient toinitiate Li dendrite penetration.

The electrolyte glass sheet can have physical dimensions and featuressuitable or particularly adapted for service as a separator in a batterycell. For example, the sheet can have a variety of areas such that itdoes not constrain battery cell format. It can have a substantiallyuniform thickness of no more than 100 μm, either as formed or assubsequently processed. And it can have substantially parallellengthwise edges, again either as formed or as subsequently processed.The electrolyte glass sheet can also be configured as a flexible roll tofacilitate storage and processing, for example a continuous web at least100 cm in length.

In some embodiments, the sheet is characterized as an inorganic vitreoussulfide-based glass sheet. The vitreous sheet may be furthercharacterized as having a threshold current for lithium dendriteinitiation that is greater than 1 mA/cm².

Characterization of thermal, and associated viscosity, properties of aglass may be made with reference to the glass stability factor{T_(x)−T_(g)}, which is the separation of the onset of crystallization(T_(x)) and the glass transition temperature (T_(g)). Sulfur-based glasscompositions that are less prone to crystallization and/or have highermelt viscosities, and therefore a higher glass stability factor, butstill retain a requisite level of Li ion conductivity (>10⁻⁵ S/cm) havebeen developed. While apparently counterintuitive to decrease thelithium ion conductivity of a glass that is specifically intended foruse in a battery cell as a lithium ion conductor, in various embodimentsthis approach is contemplated for making and improving properties of thevitreous glass solid electrolyte sheets. Accordingly, in variousembodiments the composition of a suitable sulfide-based glass system isadjusted to enhance thermal properties, even at the sacrifice of reducedconductivity, so that an electrolyte glass sheet as described andclaimed may be obtained where the glass has a stability factor{T_(x)−T_(g)}<100° C.; or less than 50° C.; or even less than 30° C.

In some embodiments, the sulfide-based glass is of a type Li₂S—YS_(n);Li₂S—YS_(n)—YO_(n) and combinations thereof, wherein Y is selected fromthe group consisting of Ge, Si, As, B, or P, and n=2, 3/2 or 5/2, andthe glass is chemically and electrochemically compatible in contact withlithium metal. Suitable glass may comprise Li₂S and/or Li₂O as a glassmodifier and one or more of a glass former selected from the groupconsisting of P₂S₅, P₂O₅, SiS₂, SiO₂, B₂S₃ and B₂O₃. In someembodiments, the glass may be devoid of phosphorous.

In another aspect, a method of making a standalone lithium ionconductive solid electrolyte is provided. The method involves drawing amolten sheet of lithium ion conducting sulfide glass into a freestandinginorganic vitreous sheet of sulfide-based lithium ion conducting glass.

In still another aspect, another method of making a standalonelithium-ion conductive solid electrolyte is provided, the methodinvolving providing a lithium ion conducting sulfide glass pre-form, andpulling on the preform at a temperature sufficient to draw the pre-formto a ribbon having a thickness in the range of 5 to 100 um.

In other aspects, the standalone sulfide based lithium ion-conductiveglass solid electrolyte may be disposed in a battery cell component as aseparator adjacent a negative lithium electroactive layer, or in abattery cell as a separator between a positive electrode and a negativelithium electroactive layer.

This and other aspects are described in further detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-D illustrate a freestanding Li ion conducting solid electrolytesheet of this disclosure.

FIGS. 1E-F illustrate a freestanding Li ion conducting solid electrolytesheet of this disclosure and a mother-sheet from which it iscut-to-size.

FIG. 2 illustrates surface defects at the interface between asulfide-based glass and Li metal.

FIG. 3A illustrates a continuous roll of the instant solid electrolytesheet wound on a spool.

FIG. 3B illustrates a continuous roll of a freestanding Li ionconducting solid electrolyte sheet in the form of a web from whichindividual discrete solid electrolyte sheets are excised and stacked.

FIGS. 4A-D illustrate apparatus for making a freestanding Li ionconducting solid electrolyte sheet in accordance with variousembodiments of this disclosure: FIGS. 4A-B illustrate a fusion drawapparatus; FIG. 4C illustrates a slot draw apparatus; and FIG. 4Dillustrates a preform draw apparatus.

FIGS. 5A-C illustrate flowcharts for methods of making a continuousfreestanding Li ion conducting solid electrolyte inorganic vitreousglass sheet of this disclosure.

FIG. 6 illustrates a fabrication system and method for making acontinuous web of a freestanding Li ion conducting solid electrolytesheet in accordance with this disclosure in the form of a continuousroll; the web configured using an inline sheet to roll process.

FIGS. 7A-B illustrate electrode subassemblies in accordance with variousembodiments of this disclosure.

FIG. 8A illustrates a cross sectional depiction of a lithium metalelectrode assembly in accordance with this disclosure.

FIG. 8B illustrates a method of making a lithium metal electrodeassembly in accordance with various embodiments of this disclosure.

FIGS. 8C-G illustrate cross sectional depictions of lithium metalelectrode assemblies, in accordance with various embodiments of thisdisclosure.

FIG. 9 illustrates a positive electrode assembly in accordance with thisdisclosure.

FIGS. 10A-E illustrate battery cells in accordance with variousembodiments of this disclosure. In various embodiments the battery cellis a solid-state cell; a cell having a common liquid electrolyte; ahybrid cell having lithium metal electrode assembly of this disclosure;a constructed with a lithium metal free laminate; and a hybrid cellhaving a positive electrode assembly of this disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to specific embodiments of thedisclosure. Examples of the specific embodiments are illustrated in theaccompanying drawings. While the disclosure will be described inconjunction with these specific embodiments, it will be understood thatit is not intended to limit the disclosure to such specific embodiments.On the contrary, it is intended to cover alternatives, modifications,and equivalents as may be included within the spirit and scope of thedisclosure. In the following description, numerous specific details areset forth in order to provide a thorough understanding of the presentdisclosure. The present disclosure may be practiced without some or allof these specific details. In other instances, well known processoperations have not been described in detail so as to not unnecessarilyobscure the present disclosure.

A standalone lithium ion-conductive solid electrolyte in accordance withthis disclosure can include a freestanding inorganic vitreous sheet ofsulfide-based lithium ion conducting glass capable of high performancein a lithium metal battery by providing a high degree of lithium ionconductivity while being highly resistant to the initiation and/orpropagation of lithium dendrites. Such an electrolyte is also itselfmanufacturable, and readily adaptable for battery cell and cellcomponent manufacture, in a cost-effective, scalable manner.

With reference to FIGS. 1A-F there are illustrated freestanding vitreoussheets of sulfide-based lithium ion conducting glass 100 in accordancewith various embodiments of this disclosure, as described herein. Theglass electrolyte sheets are highly conductive of Li ions, withintrinsic room temperature Li ion conductivity ≥10⁻⁵ S/cm, preferably≥10⁻⁴ S/cm, and more preferably ≥10⁻³ S/cm. Moreover, the sheets havephysical dimensions and features suitable or particularly adapted forservice as a separator in a battery cell, including substantiallyuniform thickness (t) of no more than 100 μm, scalability to longcontinuous lengths (e.g., >50 cm) and large areas (e.g., >100 cm²),manufacturably adjustable area aspect ratios, and flexibilitycommensurate with winding.

By “substantially uniform thickness” it is generally meant that thethickness of the referenced article is sufficiently uniform for itsintended purpose; for example the thickness of the solid electrolytesheet is sufficiently uniform for its intended purpose as a solidelectrolyte sheet in a battery cell. When using the term “uniformthickness” (e.g., with respect to the thickness of the solid electrolytesheet or a fluid stream of glass) it is meant that the thicknessvariation is at most 20% of the average thickness (t), and morepreferably less. In embodiments, wherein the average thickness is 250μm≤t<500 μm, the thickness variation is preferably ≤2%, and morepreferably ≤1%; in embodiments wherein the average thickness is 100μm≤t<250 μm, the thickness variation is preferably ≤5%, and morepreferably ≤2%; in embodiments wherein the average thickness is 50μm≤t<100 μm the thickness variation is preferably ≤10%, and morepreferably ≤5%, and more preferably ≤2%; in embodiments wherein theaverage thickness is 10 μm≤t<50 μm the thickness variation is preferably≤20%, more preferably ≤10%, even more preferably ≤5%; and yet even morepreferably ≤2%; and in embodiments wherein the average thickness is 5μm≤t<10 μm the thickness variation is preferably ≤20%, more preferably≤10%, and even more preferably ≤5%.

In particular embodiments, glass sheet 100 is formed as a long flexibleribbon with substantially parallel lengthwise edges, and length (l) towidth (w) area aspect ratio (l/w)≥10, and therefore suitable as acontinuous separator in a battery cell with a wound or foldedconstruction. Preferably, the ribbon is sufficiently robust when flexedto have a bending radius ≤10 cm, preferably ≤5 cm, more preferably ≤2.5cm, even more preferably ≤1 cm, and yet even more preferably ≤0.5 cm,and thus capable of being wound as such without fracture.

In various embodiments sheet 100 has substantially parallel lengthwiseedges and an area footprint ≥10 cm², ≥25 cm², ≥50 cm², ≥100 cm², or≥1000 cm². In various embodiments, sheet 100 has length dimension ≥10cm, ≥20 cm, ≥30 cm, ≥50 cm, or ≥100 cm. In various embodiments, thewidth dimension of the sheet is between 1 to 5 cm (e.g., about 1 cm,about 2 cm, about 3 cm, about 4 cm, or about 5 cm wide) or between 5 to10 cm (e.g., about 5 cm, or about 6 cm, or about 7 cm, or about 8 cm orabout 9 cm, or about 10 cm wide). In various embodiments the solidelectrolyte sheet is in the shape of a thin ribbon having length (l)≥10cm, width (w) between 1 to 10 cm, and area aspect ratio (l/w)≥10, or≥20. The sheet may be cut into pieces of any suitable size for use, suchas a separator in into a battery cell or component.

Continuing with reference to FIGS. 1A-F, sheet 100 is embodied as afreestanding inorganic vitreous glass sheet that is not surrounded orsupported by a substrate, and thus sheet 100 is substrate-less andcapable of being stored, transported and integrated into battery cellmanufacturing processes as a standalone solid electrolyte separator orcell component. By use of the term freestanding when referring to thesulfide glass sheet, it is meant that the sheet is a self-supportinglayer of substantially uniform sulfide glass composition. Accordingly,in various embodiments a freestanding solid electrolyte sheet issubstrate-less. By use of the term standalone (e.g., “standalonevitreous glass sheet” or “standalone lithium ion-conductive solidelectrolyte”) it is meant that the referenced material or article (e.g.sheet or electrolyte) is a discrete battery cell component, and thus isnot, or has not yet been incorporated in a battery cell or an electrodeassembly.

In various embodiments, sheet 100 is fabricated to ensure that it issubstantially impervious to liquids that it may contact during operationof a device in which it is incorporated, such as a liquid electrolyte ina battery cell. Accordingly sheet 100 should be free (i.e., devoid) ofthrough porosity including pinholes or defects that would allow a liquidelectrolyte to seep across the sheet. In other embodiments liquidimpermeability is not a requisite property of the solid electrolytesheet; for instance, sheet 100 incorporated as a separator in a fullysolid-state Li-ion battery cell. In such cases the sheet 100 maynevertheless be substantially impenetrable, by which it is meant, as itpertains to lithium metal dendrites within the context of the describedsolid electrolytes configured in a lithium battery cell, that over theservice life of the battery cell, lithium metal dendrites are unable topenetrate across the sheet, and preferably cannot extend deeply or atall into the bulk of the solid electrolyte sheet (e.g., beyond 10% ofthe sheet thickness), and in this way the referenced battery cell isresistant to electrical shorting and fracture that might otherwiseresult from dendritic in-growth of lithium metal into pre-existing flawsor microstructural features on or nearby the sheet surface.

In various embodiments, sheet 100 is fabricated to be highly resistantagainst initiation and propagation of lithium dendrites. Withoutintending to be limited by theory it is believed that the ability of thesolid electrolyte sheet to resist and preferably prevent dendriticthrough penetration in a lithium battery cell is based on itsfabrication as a vitreous glass with liquid-like surfaces, by which itis meant a smooth amorphous surface, as resulting from the action ofsurface tension on a quiescent liquid. And by vitreous it is meant aglass derived from a continuous solidified glass melt (e.g., as opposedto a powder compact), and therefore lacking powder particle,inter-particle boundary, and contiguous void manifestations of a pressedpowder compact extending between the first and second principal surfacesof the glass sheet, and the liquid-like surface lacks flawmanifestations of a pressed powder compact that are sufficient toinitiate Li dendrite penetration. Preferably the liquid-like surface ofthe vitreous sheet is essentially free of crystalline phases and ofexceptionally smooth topography, having an average surface roughnessR_(a)<0.1 um, preferably <0.05 um, more preferably R_(a)<0.01 um, andeven more preferably R_(a)<0.005 um, and yet even more preferablyR_(a)<0.001 um.

In various embodiments, solid electrolyte sheet 100 is excised from thehigh quality center portion of a mother-sheet. For instance, withreference to FIGS. 1 E-F, there is illustrated a mother-sheet ofvitreous Li ion conducting monolithic sulfur-containing glass made, forinstance, by melt downdraw or preform-draw. Mother-sheet 100M may becharacterized as having a high quality center region (or portion) 105and lower quality edge portions 107, and solid electrolyte sheet 100 isexcised from the mother sheet by removing the edge portion(s) 107;typically, by cutting (e.g., by scoring, or slicing the edges off with alaser beam or wire saw). Generally, mother-sheet 100M is annealed toremove stresses prior to slicing off the low quality edge portions, asillustrated in FIG. 1F. Moreover, to ensure utmost quality, peripheralportions of the high quality center region 105 x may also be removed bythe lengthwise cutting procedure.

Preferably the high quality center portion of mother-sheet 100M hassufficient surface quality to circumvent the need to perform apost-solidification polishing step. For instance, in variousembodiments, the major opposing surfaces of the high quality centerportion of mother-sheet 100M has an average surface roughness R_(a)≤1.0μm, preferably ≤0.5 μm, more preferably R_(a)≤0.2 μm, R_(a)≤0.1 μm,R_(a)≤0.05 μm, and even more preferably R_(a)≤0.05 μm, and yet even morepreferably R_(a)≤0.01 μm.

In addition to high surface quality, as described above, preferably thethickness and thickness uniformity of high quality center portion 107 isof a pre-determined value, thereby circumventing the extra processingstep of grinding down the surface(s) or slicing within the plane of thesheet, or even more generally removing material from surfaces 101A/101Bin order to achieve the desired thickness and thickness uniformity ofsolid electrolyte sheet 100.

In various embodiments, in addition to having high surface qualityand/or a pre-determined and uniform thickness the major surfaces of thehigh quality center portion of mother-sheet 109 is preferably chemicallyand physically pristine in its virgin state, and thus untouched by aforeign solid surface upon solidifying.

The vitreous solid electrolyte glass sheet of this disclosure addressesnumerous shortcomings of pressed/hot-pressed sulfide glass powdercompacts, polycrystalline ceramic membranes (e.g., garnets), and solidpolymer electrolyte films (e.g., PEO-like).

For example, powder compaction is fraught with mechanical andelectrochemical complications related to surface flaws, inter-particleboundaries and an undue density of void-like defects, which act asstress concentrators that limit strength, thwart flexibility and serveas Li dendrite initiators and facile pathways for dendritic shorting.And while simultaneous heating and pressing (i.e., hot pressing) at highpressures for extended times can be useful for improving inter-particlecohesion, it adds a costly additional step that complicates processingand does not adequately address surface flaws related to dendriteinitiation, as further described below. Moreover, powder compaction,while suitable for making small pressed pellets, is a batch process thatis not scalable, and cannot be used to make long flexible sheets ofglass.

Mechanical failure of any glass (e.g., window glass) will occur when thestress and defect size reach a critical combination. The reliability istherefore statistical, but nonetheless related to the largest sizedflaws on the surface. In contrast, small shallow flaws are perceived asless important, since the underlying mechanical strength of the sheet islargely unaffected by their existence. When shallow flaws are small innumber density, or even singular, their very existence is generallyconsidered insignificant from a practical perspective.

At practical current densities however, as described further herein, ashallow flaw at an otherwise liquid-like surface can be prohibitive forrealizing a dendrite resistant solid electrolyte glass sheet, if theflaw depth is beyond a threshold size for dendrite initiation. Withreference to FIG. 2, in a lithium metal battery cell, wherein a vitreoussolid electrolyte sheet 100 is in contact with a solid Li metal layer210, a flaw extending beyond a threshold depth can create a highlylocalized hot spot for current focusing, which can lead to very highlocal current densities and dendritic penetration of Li metal into thesheet during cell charging, even for electrolytes with elastic moduliwell above 20 GPa.

The threshold flaw depth is determined by several factors, including thedetailed flaw geometry, the effective fracture toughness of theelectrolyte, K_(lc) ^(eff) which is typically less than the fracturetoughness determined from a mechanical fracture test, K_(lc), the sheetthickness (t), and the local current density, I_(local), which in turnis proportional to the nominal lithium anode current density,I_(nominal). The general functional relationship for the nominal lithiumanode current densities, I_(thr), may be expressed asI _(thr) =f(K _(lc) ^(eff) ,t/(Γ,ν,I _(local)))

where

-   -   K_(lc) ^(eff) is the effective fracture toughness at the flaw        tip where flaw extension most readily occurs    -   Γ is the deepest flaw extension into the solid electrolyte    -   t is the sheet thickness    -   ν is the viscosity or the equivalent flow stress (both        temperature dependent) of the solid lithium, and    -   I_(local) is the solid electrolyte/lithium metal anode interface        current density in the immediate vicinity of the surface flaw.        Typically I_(local)>I_(nominal).

To mitigate dendrite propagation through a solid electrolyte sheethaving a liquid-like surface in direct contact with a solid Li metallayer, the deepest flaw extension Γ into the sheet should be less than1% of the sheet thickness, and preferably less than 0.1%, and generallyno more than 5 μm. For example, the deepest flaw extension in a 100 μmthick sheet should be less than 1 μm, and preferably less than 0.1 μm;and for a 50 μm thick sheet it should be less than 0.5 μm, andpreferably less than 0.05 μm.

Moreover, threshold current densities associated with dendriteinitiation can be determined experimentally, or can be estimated fromanalytical approximations to the associated fracturemechanics-electrochemical problem. Typical experiments onpolycrystalline solid electrolytes in direct contact with solid Li metalanodes have typically shown threshold charging current densities fordendrite initiation below 0.5 mA/cm². In contrast, vitreous sulfidesolid electrolytes with smooth interfaces, such as prepared by themethods contemplated herein, have surprisingly sustained currentdensities in excess of 2 mA/cm² without dendrite penetration, whencycling 2 mAh/cm² of lithium metal for over 50 cycles. Subject to theseprinciples, the inventors are now able to characterize the surfacequality of the sheet based on experimentally determined values forI_(thr), by cycling a solid Li metal layer against the solid electrolytesheet at 1 mAh/cm² for at least 50 charge cycles without propagating adendrite across the sheet. In various embodiments the solid electrolytesheet is characterized as having a surface quality commensurate with anI_(thr) no less than 1 mA/cm², preferably no less than 2 mA/cm², morepreferably I_(thr) is no less than 3 mA/cm², even more preferablyI_(thr) is no less than 4 mA/cm², and yet even more preferably I_(thr)is no less than 5 mA/cm².

Considering the sensitivity of dendrite initiation to the presence ofshallow flaws, in order for the vitreous solid electrolyte sheet toretain its I_(thr) value during handling and downstream processing ofcell components and cells, special care should be given to minimizecontact damage.

Vitreous Web of Solid Electrolyte Sulfide Glass

With reference to FIG. 3A, in various embodiments the solid electrolytesheet may be of sufficient flexibility, length and manufacturability tobe fabricated as a continuous web of vitreous inorganic Li ionconducting sulfide glass 100W, having a length typically greater than 50cm, and preferably greater than 100 cm, and even more preferably greaterthan 1000 cm long. In various embodiments, glass web 100W serves a solidelectrolyte substrate-sheet for the formation of downstream battery cellcomponents, including electrode subassemblies, electrode assemblies, andbattery cells of this disclosure.

As illustrated in FIG. 3A, in various embodiments web 100W issufficiently flexible that it may be formed into a continuous roll 100Rwithout fracture, and typically wound on a support spool 301 for storageand/or transportation. Preferably continuous web 100W has bending radius≤100 cm, and preferably ≤50 cm, more preferably ≤10 cm, even morepreferably ≤5 cm, and yet even more preferably ≤2.5 cm, and thus capableof being wound as such without fracture. In various embodiments thespool or drum has a diameter in the range of 100 cm-200 cm; or 50 cm to100 cm; or 20 to 50 cm; or 10 cm to 20 cm; or 5 cm to 10 cm; or 2.5 cmto 5 cm. In various embodiments continuous roll 100R serves as a supplyroll or a source roll for R₂R manufacture or roll-to-sheet processing ofdownstream battery cell components and battery cells.

As illustrated in FIG. 3B, in various embodiments, multiple discretesolid electrolyte sheets 100Z (e.g., a stack of solid electrolytesheets) may be excised (i.e., cut to size) from Li ion conducting glassweb 100W. The sheet may be cut into pieces of any suitable size for use,such as a separator in into a battery cell or component. In variousembodiments, web 100W yields at least 5 discrete solid electrolytesheets having length of at least 10 cm, preferably at least 10 suchsheets, more preferably at least 50 such sheets, and even morepreferably at least 100 such sheets.

In various embodiments, to facilitate winding, storage and/or use of asupporting spool, a protective material interleave (not shown) may bedisposed between adjacent layers of the source roll in order to preventthe opposing web surfaces from contacting each other. Generally, theprotective interleave is not a lithium ion conductor. In variousembodiments the interleave may be a porous polymer layer (e.g.,micro-porous) or a dry swellable polymer layer (i.e., a dry gellablepolymer layer), suitable to serve as both interleave in the source rolland as a porous or gel battery separator component in a battery cell.

Thermal Parameters

Recognizing the benefit of perfecting the sulfide glass into a vitreousglass sheet, as opposed to a powder construct, methods and modifiedsulfur-containing glass compositions that are less prone tocrystallization and/or have higher melt viscosities but still retain arequisite level of Li ion conductivity (>10⁻⁵ S/cm) have been developed.In particular, methods of increasing the glass stability factor and/orHruby parameter, including increasing the amount of oxygen in the glass,increasing the oxygen to sulfur mole ratio, increasing the amount ofoxide network former in the glass, increasing the ratio of oxide networkformer to sulfide network former, incorporating intermediate networkformers, decreasing the amount of bond breaking lithium ions, tuning thecomposition of the base sulfide glass to have more than 4 main elementalconstituents (e.g., 5 main elemental constituents: S, Li, B, P, and O)or more than 5 main elemental constituents (e.g., 6 main elementalconstituents: S, Li, Si, B, P, and O) and combinations thereof aredescribed. In addition, additives to the base glass are alsocontemplated for use herein as devitrifying agents and crystallizationinhibitors.

Moreover, while apparently counterintuitive to decrease the Li ionconductivity of a glass that is specifically intended for use in abattery cell as a Li ion conductor, in various embodiments this is theapproach contemplated herein for making and improving properties of thevitreous solid electrolyte glass sheets of this disclosure. Accordingly,in various embodiments the composition of the sulfide base glass systemis adjusted to enhance thermal properties at the sacrifice of reducedconductivity.

A number of terms are used in the description for discussing the thermalproperties of the glass. {T_(x)−T_(g)} is the difference between theonset of crystallization (T_(x)) and the glass transition temperature(T_(g)), and is also referred to herein as the glass stability factor;{T_(n)−T_(x)} is the difference between the temperature at which theglass is drawn (T_(n)) and the onset of crystallization. The liquidustemperature is (T_(liq)). The melting temperature of the glass is(T_(m)). The strain temperature is the temperature at which theviscosity of the glass is approximately 10^(14.6) poise, and stressesmay be relieved in hours. The annealing temperature is the temperatureat which the viscosity is approximately 10^(13.4) poise, and stresses ina glass may be relieved in less than 1 hour or minutes. And finally, thesoftening temperature is defined as the temperature at which the glasshas viscosity of ˜10^(7.6) poise. The glass is usually suitable fordrawing at or above this temperature.

Several techniques exist for the measurement of these characteristictemperatures. Differential scanning calorimetry (DSC) and differentialthermal analysis (DTA) are the most common. Generally, a largeseparation between T_(x) and T_(g) (i.e., a large glass stabilityfactor) is desirable for drawing glass.

Another method of determining or estimating glass stability is throughthe Hruby parameter (H_(r) parameter), as given by the followingequation:

${H\; r} = \frac{{T\; x} - {T\; g}}{{T\; m} - {T\; c}}$

A high value of H_(r) suggests high glass stability, and the larger, themore stable the glass against crystallization. For example, a glasshaving H_(r)<1, is generally highly prone to crystallization andconsidered unstable.

Vitreous Sulfide Glass Composition

In accordance with the disclosure, the Li ion conducting vitreous glasshas room temperature intrinsic Li ion conductivity ≥10⁻⁵ S/cm,preferably ≥10⁻⁴ S/cm, and more preferably ≥10⁻³ S/cm. By use of theterm intrinsic when referring to the ionic conductivity of a material itis meant the inherent conductivity of the material itself, in theabsence of any other additional material agents, such as, for example,liquid solvents or organic molecules or organic material phases. Toachieve this level of conductivity in an inorganic amorphous materialphase, sulfide based Li ion conducting glasses are particularly suitable(i.e., sulfur-containing glasses). Without intending to be limited bytheory, compared to oxygen, sulfur is found to be a highly desirableelement of the material phase. Sulfur is generally more polarizable thanoxygen, and this tends to weaken the interaction between glass formingskeletal ions and mobile lithium ions, which in turn enhances lithiumion mobility and increases associated ionic conductivity. Accordingly,in various embodiments the material phase has a glass skeleton composedin part of sulfur and through which Li ions move. Without intending tobe limited by theory, sulfur may serve several roles, includingcross-linking sulfur that forms the glass structure and non-crosslinkingsulfur that combines terminally with mobile Li ions.

Accordingly, in various embodiments the continuous amorphous materialphase of solid electrolyte sheet 100 is an inorganic sulfide based glasscomprising S (sulfur) as a main constituent element, Li (lithium) as amain constituent element and further comprising one or more M₁ mainconstituent elements selected from the group consisting of P(phosphorous), B (boron), Al (aluminum), Ge (germanium), Se (selenium),As (arsenic), O (oxygen) and Si (silicon).

In embodiments, the sulfide based solid electrolyte material furthercomprises O (oxygen) as a constituent element (e.g., typically as asecondary constituent element). In other embodiments, the amorphoussulfide glass is a non-oxide, and thus substantially devoid of oxygen asa constituent element. Typically the mol % of Li in the glass issignificant, and in particular embodiments the mole percent of Li in theglass is at least 10 mol %, and more typically at least 20 mol % or atleast 30 mol %; in some embodiments it is contemplated that the molepercent of Li in the glass is greater than 40 mol % or greater than 50mol % or even greater than 60 mol %. In various embodiments the glass isdevoid of alkali metal ions other than Li.

In various embodiments as a main constituent element of the glass,sulfur (S) is present to at least 10 mol %, and typically significantlyhigher; for instance, ≥20 mol % of S, or ≥30 mol % of S, or ≥40 mol % ofS. In various embodiments the concentration of sulfur as a mainconstituent element in the glass is between 20-60 mol %, or between30%-50 mol % (e.g., about 25 mol %, about 30 mol %, about 35 mol %,about 40 mol %, about 45 mol %, or about 50 mol %). In variousembodiments sulfur is the major elemental constituent of the glass,which is to mean the mol % of sulfur is greater than that of any otherconstituent element.

Various Li ion conducting sulfur based glasses (i.e., sulfur-containingglasses) are contemplated for use herein. These include lithiumphosphorous sulfide, lithium phosphorous oxysulfide, lithium boronsulfide, lithium boron oxysulfide, lithium boron phosphorous oxysulfide,lithium silicon sulfide, lithium silicon oxysulfide, lithium germaniumsulfide, lithium germanium oxysulfide, lithium arsenic sulfide, lithiumarsenic oxysulfide, lithium selenium sulfide, lithium seleniumoxysulfide, lithium aluminum sulfide, lithium aluminum oxysulfide, andcombinations thereof.

In various embodiments the sulfur glass, in addition to the main glassconstituent elements, includes certain additives and compounds toenhance conductivity, such as halide salts (e.g., LiCl, LiBr, LiI),aluminum (e.g., aluminum oxide as an intermediate network former),Ga₂S₃, Al₂S₃, nitrogen (e.g., thio-nitrides), as well as phosphate(e.g., lithium phosphate (e.g., Li₃PO₄, LiPO₃), sulfate (e.g., Li₂SO₄),silicate (e.g., Li₄SiO₄) and borate salts (e.g., LiBO₃). In embodiments,various devitrifying agents may be added to the sulfide glass to enhanceits stability against crystallization.

The sulfur-based glasses are sometimes described herein within thecontext of the glass system to which they belong, and roughly based onthe stoichiometry of the materials incorporated in the glass as main andsecondary elemental constituents, without reference to additives.

In various embodiments the sulfide glass system is of a type Li₂S—YS_(n)wherein Y is a glass former constituent element and may be Ge, Si, As,B, or P; and wherein n=2, 3/2 or 5/2. For example, in variousembodiments the glass system may be Li₂S—PS_(5/2) or Li₂S—BS_(3/2) orLi₂S—SiS₂. In various embodiments the glass system may be a combinationof two or more such systems; for example, Li₂S—PS_(5/2)—BS_(3/2) orLi₂S—PS_(5/2)—SiS₂ or Li₂S—PS_(5/2)—BS_(3/2)—SiS₂.

In various embodiments the sulfide glass system is of a typeLi₂S—YS_(n)—YO_(n) wherein Y is a glass former constituent element, andmay be Ge, Si, As, B, or P; and wherein n=2, 3/2 or 5/2. For example, invarious embodiments the glass system may be Li₂S—PS_(5/2)—PO_(5/2) orLi₂S—BS_(3/2)—BO_(3/2) or Li₂S—SiS₂—SiO₂.

In various embodiments the sulfide glass system is of a typeLi₂S—Y¹S_(n)—Y²O_(m) wherein Y¹ and Y² are different glass formerconstituent elements, and may be Ge, Si, As, B, or P; and wherein n=2,3/2 or 5/2 and m=2, 3/2 or 5/2, as appropriate based on the commonstandard valence of the constituent element. For example, in variousembodiments the glass system may be Li₂S—PS_(5/2)—BO_(3/2) orLi₂S—BS_(3/2)—PO_(5/2) or Li₂S—PS_(5/2)—SiO₂.

In various embodiments the glass system may be a combination of two ormore such systems of the type Li₂S—YS_(n) and Li₂S—Y¹S_(n)—Y²O_(m);wherein Y is a glass former constituent element, and may be Ge, Si, As,B, or P; Y¹ and Y² are different glass former constituent elements, andmay be Ge, Si, As, B, or P; and wherein n=2, 3/2 or 5/2 and m=2, 3/2 or5/2, as appropriate based on the common standard valence of theconstituent element.

In various afore said embodiments, Li₂S may be wholly or partiallysubstituted for by Li₂O.

Specific sulfur-based glass systems contemplated are of the typeLi₂S—YS_(n); Li₂S—YS_(n)—YO_(n) and combinations thereof; for whichY═Ge, Si, As, B, and P; and n=2, 3/2, 5/2. Specific systems includeLi₂S—P₂S₅; Li₂S—B₂S₃; Li₂S—SiS₂; Li₂S—P₂S₅—P₂O₅; Li₂S—P₂S₅—P₂O₃;Li₂S—B₂S₃—B₂O₃; Li₂S—P₂S₅—B₂S₃; Li₂S—P₂S₅—B₂S₃—B₂O₃; Li₂S—B₂S₃—P₂O₅;Li₂S—B₂S_(s)—P₂O₃; Li₂S—SiS₂—P₂O₅; Li₂S—P₂S₅—SiO₂;Li₂S—P₂S₅—P₂O₅—B₂S₃—B₂O₃ and combinations thereof.

The continuous Li ion conducting inorganic glass may be described ashaving a glass network former that brings about the skeletal lattice anda glass network modifier, such as a lithium compound, that introducesionic bonds and thereby serves as a disrupter of the lattice andprovides mobile lithium ions for conduction. In various embodimentsadditional network formers may be incorporated in the glass. Forinstance, in various embodiments the glass system may have the generalformula:xNET(major former):yNET(minor former):zNET(modifier)

-   -   wherein z=1−(x+y)

NET(major former) is the major glass network former and its molefraction, x, is the largest of all the network formers used to make theglass. Net(minor former) represents one or more minor glass networkformers that is present in the glass with mole fraction, y. In allinstances the mole fraction of the major glass former is larger thanthat of any minor glass former. However, the combined mole fraction ofthe minor glass formers may be greater than that of the major glassformer. NET(modifier) is generally Li₂S or Li₂O or some combinationthereof.

The network former (major or minor) may be a compound of the typeA_(a)R_(b), or a combination of two or more different compounds of thistype. For instance, A may be Silicon, Germanium, Phosphorous, Arsenic,Boron, Sulfur and R may be Oxygen, Sulfur, or Selenium; and the networkmodifier may be of the type N_(m)R_(c), with N being Lithium and R beingOxygen, Sulfur, or Selenium; and a, b, m, and c represent the indicescorresponding to the stoichiometry of the constituents.

In various embodiment the major network former is B₂S₃, P₂S₅ or SiS₂,and the minor network former is one or more of B₂O₃, P₂O₅, P₂O₃, SiO₂,B₂S₃, P₂S₅, SiS₂, Al₂S₃, Li₃PO₄, LiPO₃ Li₂SO₄ LiBO₃. Specific examplesinclude: i) Li₂S as the network modifier, B₂S₃ as the major former, andone or more minor formers selected from the group consisting of B₂O₃,P₂O₅, P₂O₃, SiO₂, P₂S₅, SiS₂, Al₂S₃, Li₃PO₄, LiPO₃ Li₂SO₄ LiBO₃; ii) i)Li₂S as the network modifier, P₂S₅ as the major former, and one or moreminor formers selected from the group consisting of B₂O₃, P₂O₅, P₂O₃,SiO₂, B₂S₃, SiS₂, Al₂S₃, Li₃PO₄, LiPO₃ Li₂SO₄ LiBO₃; iii) Li₂S as thenetwork modifier, SiS₂ as the major former, and one or more minorformers selected from the group consisting of B₂O₃, P₂O₅, P₂O₃, SiO₂,P₂S₅, B₂S₃, Al₂S₃, Li₃PO₄, LiPO₃ Li₂SO₄ LiBO₃. In various embodiments,the network modifier is Li₂S or Li₂O, or some combination thereof.

Selecting the appropriate sulfide glass composition depends on the endof use of the solid electrolyte sheet, and ultimately on the type andapplication of the battery cell in which it is intended to operate.Among the many potential considerations are form factor, cellconstruction, cost, power requirements, and service life. Accordingly,the glass composition may be adjusted to enhance one or more of i)chemical and electrochemical compatibility of the glass in directcontact with Li metal and/or a liquid electrolyte; ii) flexibility,shape and size; iii) glass formability (especially as it relates tothermal properties); and iv) Li ion conductivity. Optimizing one or moreof these parameters generally requires a tradeoff.

In various embodiments the sulfide glass system is selected for itschemical and electrochemical compatibility in direct contact withlithium metal.

Chemical compatibility to Li metal is an attribute that relates to thekinetic stability of the interface between glass sheet 100 and a lithiummetal layer, and electrochemical compatibility generally assesses theability of that interface to function in a battery cell. Both propertiesrequire the formation of a solid electrolyte interphase (SEI) that stopsreacting with the glass surface once formed (i.e., chemicalcompatibility) and is sufficiently dense and conductive that itsinterface resistance is acceptable for its use in a battery cell.

Incorporating certain constituent elements into glass sheet 100 isdesirable for creating an SEI commensurate with both chemical andelectrochemical compatibility. In various embodiments, phosphorous isincorporated as a main constituent element for producing an effectiveSEI, as phosphorous in direct contact with lithium metal reacts to formlithium phosphide (e.g., Li₃P), a compound highly conductive of Li ionsand fully reduced. To form an acceptable SEI, phosphorous may be presentin small amount (e.g., as a secondary constituent of the glass). Addingphosphorous as a secondary constituent element provides an effectivemethod for reducing resistance at the interface, and may be used toeffect compatibility in a glass system, which, in the absence ofphosphorous does not form a stable SEI, such as silicon sulfide glasssystems with SiS₂ or SiO₂ as a primary network former. In otherembodiments, however, Si may be intentionally excluded as a constituentelement of sulfide glass sheet 100.

Notably, it has been discovered that phosphorous sulfide glass systemsare not the only glasses chemically and electrochemically compatibilityin direct contact with Li metal. Surprisingly, boron sulfide glasses,even in the absence of phosphorous, have shown remarkable chemical andelectrochemical compatibility against metallic lithium. Accordingly, invarious embodiments phosphorous may be excluded from the glass as aconstituent element, mitigating potential issues associated with highvapor pressure of the melt and chemical reactivity. However, in smallamount, adding phosphorous as a secondary constituent element to theboron sulfide glasses should not impart processing issues, and may beused, as described below, as a method for reducing resistance at the Limetal solid electrolyte interface.

In various embodiments adding oxygen and silicon provides a method forimproving thermal properties, especially for enhancing glassformability, including glass stability (e.g., increasing the glassstability factor and/or Hruby parameter) and/or viscosity at theliquidus temperature (T_(liq)). For instance, adding silicon as asecondary constituent to a phosphorous sulfide or boron sulfide glassprovides a method for increasing glass stability and/or viscosity atT_(liq), while retaining compatibility to Li metal. The addition ofoxygen as a constituent element may also afford benefit in theseregards. In various embodiments oxygen may be incorporated as a main orsecondary constituent element in lithium phosphorous sulfide and lithiumboron sulfide glass systems as a method for increasing the glassstability factor and/or Hruby parameter. For instance,xLi₂S-yP₂S₅-zSiS₂, xLi₂S-yB₂S₃-zSiS₂, xLi₂S-yP₂S₅-zSiO₂,xLi₂S-yB₂S₃-zSiO₂, xLi₂S-yB₂S3-zB₂O₃, xLi₂S-yP₂S₅-zP₂O₅; wherein withx+y+z=1 and x−0.4-0.8, y=0.2-0.6, and z ranging from 0 to 0.2 (e.g.,about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11,0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2).

Solid electrolyte sheets of silicon sulfide based glasses areparticularly advantageous for use as a separator sheet in battery cellswhich employ a common liquid electrolyte or wherein the separator sheetdoes not contact electroactive material. For instance, xLi₂S-ySiS₂;xLi₂S-ySiS₂-zSiO₂; xLi₂S-ySiS₂-yB₂S₃; xLi₂S-ySiS₂-yB₂O₃;xLi₂S-yB₂S₃-zSiO₂; wherein with x+y+z=1 and x=0.4-0.8, y=0.2-0.6, and zranging from 0 to 0.2 (e.g., about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06,0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18,0.19, 0.2).

With consideration of the above discussion, it is clear that in limitedamount certain elements can have a beneficial role for enhancingperformance of sheet 100 and/or improving glass stability forprocessing. The addition of phosphorous can reduce interfacialresistance with Li metal and the addition of oxygen can improve glassstability. In a boron sulfide glass, the addition of phosphorous, as asecondary constituent element, can be made via the incorporation of P₂S₅and the addition of oxygen via B₂O₃; yielding the glass system:Li₂S—B₂S₃—P₂S₅—B₂O₃; wherein B₂S₃ is the primary network former, P₂S₅and B₂O₃ are secondary network formers, and Li₂S is the networkmodifier. As such, the oxygen to phosphorous mole ratio can be varied.In another embodiment the phosphorous and oxygen mole ratio may beconstrained by incorporating P₂O₅ as a single ingredient, giving rise tothe glass system Li₂S—B₂S₃—P₂O₅; wherein B₂S₃ is the primary networkformer, P₂O₅ is a secondary former, and Li₂S is the network modifier.

Specific examples include, 0.7Li₂S-0.29P₂S₅-0.01P₂O₅;0.7Li₂S-0.28P₂S₅-0.02P₂O₅; 0.7Li₂S-0.27P₂S₅-0.03P₂O₅;0.7Li₂S-0.26P₂S₅-0.04P₂O₅; 0.7Li₂S-0.25P₂S₅-0.05P₂O₅;0.7Li₂S-0.24P₂S₅-0.06P₂O₅; 0.7Li₂S-0.23P₂S₅-0.07P₂O₅;0.7Li₂S-0.22P₂S₅-0.08P₂O₅; 0.7Li₂S-0.21P₂S₅-0.09P₂O₅;0.7Li₂S-0.2P₂S₅-0.1P₂O₅; 0.7Li₂S-0.29B₂S₃-0.01B₂O₃;0.7Li₂S-0.28B₂S₃-0.02B₂O₃; 0.7Li₂S-0.27B₂S₃-0.03B₂O₃;0.7Li₂S-0.26B₂S₃-0.04B₂O₃; 0.7Li₂S-0.25B₂S₃-0.05B₂O₃;0.7Li₂S-0.24B₂S₃-0.06B₂O₃; 0.7Li₂S-0.23B₂S₃-0.07B₂O₃;0.7Li₂S-0.22B₂S₃-0.08B₂O₃; 0.7Li₂S-0.21B₂S₃-0.09B₂O₃;0.7Li₂S-0.20B₂S₃-0.1B₂O₃; 0.7Li₂S-0.29B₂S₃-0.01P₂O₅;0.7Li₂S-0.28B₂S₃-0.02P₂O₅; 0.7Li₂S-0.27B₂S₃-0.03P₂O₅;0.7Li₂S-0.26B₂S₃-0.04P₂O₅; 0.7Li₂S-0.25B₂S₃-0.05P₂O₅;0.7Li₂S-0.24B₂S₃-0.06P₂O₅; 0.7Li₂S-0.23B₂S₃-0.07P₂O₅;0.7Li₂S-0.22B₂S₃-0.08P₂O₅; 0.7Li₂S-0.21B₂S₃-0.09P₂O₅;0.7Li₂S-0.20B₂S₃-0.1P₂O₅.

Methods of Making

Vitreous sulfide-based glass sheet 100 may be fabricated using anoverflow technique such as fusion draw, which uses a drawing tank andtakes advantage of gravity to allow molten glass to flow down theoutside surfaces of the tank, and in this way yield two flowing glasssurfaces which are joined to form a single flowing sheet.

With reference to the fusion draw apparatus 400A in FIGS. 4A-B, amaterial batch of Li ion conducting sulfide glass powder, which may beformed by mechanical milling, is heated in a melting vessel wherefrom itis caused to flow (via flow pipes 405) into a trough-like container 407in an amount sufficient to cause overflow of the melt 409 from bothsides of the trough. The opposing flows are then combined by fusion toform a single liquid stream of unbroken continuity 100, which may be fedto drawing equipment (e.g., via edge rollers or glass pulling rods), forcontrolling the thickness of the sheet, depending upon the rate at whichthe solidified portion of the sheet is pulled away. Accordingly, themajor surfaces of the as-solidified glass sheet, or at least its highquality center portion, are pristine, as they have not contacted anypart of the apparatus (e.g., the trough walls or flow pipes), andtherefore have superior surface quality. In various embodiments, thefusion draw process may be modified to allow for the drawing of twodissimilar glasses, one optimized for contact with lithium metal and theother optimized for a different purpose(s) or utility such as contactwith a positive electrode battery cell component (e.g., a lithiumpositive electroactive material) or a liquid phase electrolyte, or easeof processing or high conductivity. For instance, a first sulfide glassstream of unbroken continuity (e.g., having as main constituentelements: lithium, sulfur, and silicon) fused to a second sulfide glassstream (e.g., having as main constituent elements: lithium, sulfur, andone or more of boron or phosphorous).

In an alternative process, freestanding solid electrolyte sheet 100 maybe formed by slot draw to yield a substantially amorphous vitreous solidelectrolyte sheet of Li ion conducting sulfur-containing glass. Withreference to FIG. 4C, an apparatus 400C for making the freestandingsheet using a slot drawing process is illustrated. The apparatusincludes melting vessel 460, for heating and holding a material batch,typically in powder form (e.g., a powder batch of sulfide glass or abatch of raw precursor powders in proper stoichiometry for making theglass), above the batch melting temperature, and an open slot 470 nearthe bottom of the tank and through which the batch of molten glass flowsby drawing to form continuous glass sheet 100 which may be optionallypulled through rollers 480 for shaping, and optionally traversed intofurnace 490 for an annealing heat treatment, and thereafter optionallyplaced through a second set of rollers 485 and/or subjected to an edgeremoval process (as described above) to yield the solid electrolytesheet in its final or near final form.

Additional processing steps may be used to enhance the cooling rate,such as flowing a non-reactive inert fluid (e.g., ultra dry nitrogen orargon) over one or both surfaces, typically a gas (e.g., helium orargon). The cooling gas should have a very low moisture and oxygencontent, preferably less than 10 ppm.

In various embodiments vitreous solid electrolyte glass sheet 100 isformed by preform drawing, wherein a preform of the sulfide based solidelectrolyte glass is drawn (e.g., pulled) in length at a temperatureabove the glass transition temperature, to the desired shape and size.Typically, the preform is heated to a temperature at which it has lowenough viscosity to deform under its own weight, which is usually ataround the softening temperature of the glass. Upon drawing, the heatedportion starts to flow, and becomes a highly viscous fluid stream,typically in the range of 10⁴-10⁶ poise.

With reference to FIG. 4D there is shown an apparatus 400D suitable forpreform draw of a sulfide based solid electrolyte sheet of the instantdisclosure, and sometimes referred to as a redraw process. In operation,the vitreous preform 410D is heated in a deformation zone 420D and thendrawn using mechanized rollers 430D. Within the deformation zone thepreform is exposed to heat sufficient to raise its temperature aboveT_(g) but below T_(m) and preferably below T_(x), and then drawn to asheet of desired length and thickness. In some embodiments it iscontemplated that the drawing apparatus includes a flow system forflowing an inert gas nearby the drawn sheet in order to speed up coolingof the drawn sheet section, the gas preferably having a very lowmoisture and oxygen content, as described above.

The resulting cross sectional shape of the formed sheet is usuallysimilar to that of the preform from which it has been drawn. Preferably,the preform has a smooth flat surface with minimal surface roughness andwaviness. In various embodiments the preform is, itself, a vitreousglass construct. For instance, the preform may be made by molding moltenglass into a rectangular bar-like shape of substantial width andthickness typically 10 times that desired for the sheet. For example, toa draw a thin vitreous solid electrolyte ribbon in the range of 10 to500 μm thick, in various embodiments the preform is rectangular with athickness in the range of 200 μm to 1000 μm, a width of 5 to 20 cm, anda length of about 30 cm to 100 cm (e.g., a rectangular shaped bar, about5 cm wide, about 30 cm long and about 400 um thick). Methods andapparatus' for drawing a glass preform to form a substrate forsemiconductor devices and flat panel displays are described in US Pat.Pub. No.: US20070271957, US20090100874; 20150068251; all of which areincorporated by reference herein for the purpose of further describingthese glass preform methods.

With reference to FIGS. 5A-C there is illustrated flowchartsrepresentative of various methods 500A-C of making solid electrolytesheet 100 using draw processes as described above. Methods 500A-Cinclude a first step of selecting a glass composition 505. For example,the composition may be selected for suitability to the particular drawprocess of making sheet 100 (e.g., preform draw 550A from a vitreouspreform 540A to form a vitreous glass ribbon 560A and/or melt draw 550Bfrom molten glass 540B to form a vitreous glass sheet 560B).

In various methods, the step of selecting the sulfur containing glasscomposition is based on glass stability factor and conductivity; e.g.,selecting a glass composition having a glass stability factor >20° C.,or >30° C., or >40° C., or >50° C., or >60° C., or >70° C., or >80° C.or >90° C. or >100° C. and a Li ion conductivity ≥10⁻⁵ S/cm, andpreferably ≥10⁻⁴ S/cm, and more preferably ≥10⁻³ S/cm.

In various methods, the step of selecting the sulfur containing glasscomposition is based on Hruby parameter and conductivity; e.g.,selecting a glass composition having Hruby parameter >0.4, or >0.5,or >0.6, or >0.7, or >0.8, or >0.9, or >1 and a Li ion conductivity≥10⁻⁵ S/cm, and preferably ≥10⁻⁴ S/cm, and more preferably ≥10⁻³ S/cm.

In various methods the step of selecting the sulfur containing glasscomposition involves adjusting the mole percent of Li and/or S (sulfur)and/or O (oxygen) and/or Si (silicon) in the glass to achieve a Hrubyparameter of >0.5, or >0.6, or >0.7, or >0.8, or >0.9, or >1 and a Liion conductivity ≥10⁻⁵ S/cm, and preferably ≥10⁻⁴ S/cm, and morepreferably ≥10⁻³ S/cm.

In various methods the step of selecting the sulfur containing glasscomposition involves adjusting the mole percent of Li and/or S (sulfur)and/or O (oxygen) and/or Si (silicon) in the glass to achieve a glassstability factor of >50° C., or >60° C., or >70° C., or >100° C. and aLi ion conductivity ≥10⁻⁵ S/cm, and preferably ≥10⁻⁴ S/cm, and morepreferably ≥10⁻³ S/cm.

In various methods the step of selecting the sulfur containing glasscomposition involves adjusting the mole percent of O (oxygen) to withina value of 1-20 mol % to achieve a glass stability factor >50° C.,or >60° C., or >70° C., or >80° C. or >90° C. or >100° C. while stillretaining an interface resistance with a Li metal layer that is no morethan 200 Ω-cm² and preferably no more than 100 Ω-cm², and morepreferably no more than 50 Ω-cm², and even more preferably no more 25Ω-cm², or no more than 10 Ω-cm².

In various methods the step of selecting the sulfur containing glasscomposition involves adjusting the mole percent of Si (silicon) towithin a value of 1-20 mol % to achieve a glass stability factor >50°C., or >60° C., or >70° C., or >80° C. or >90° C. or >100° C. whilestill retaining an interface resistance with a Li metal layer that is nomore than 200 Ω-cm² and preferably no more than 100 Ω-cm², and morepreferably no more than 50 Ω-cm², and even more preferably no more 25Ω-cm², or no more than 10 Ω-cm².

In various methods the step of selecting the sulfur containing glasscomposition involves adjusting the mole percent of P (phosphorous) inthe glass within a value of 1-20 mol % to achieve an interfaceresistance with a Li metal layer that is no more than 200 Ω-cm², andpreferably no more than 100 Ω-cm², and more preferably no more than 50Ω-cm², and even more preferably no more 25 Ω-cm², or no more than 10Ω-cm².

In various methods, the step of selecting the glass composition includesreplacing a certain amount of sulfur in the glass with oxygen, or acertain amount of boron in the glass with silicon, the amount sufficientto increase the glass stability factor by at least 10° C. or the Hrubyparameter by at least 0.1, while maintaining a Li ion conductivity ≥10⁻⁵S/cm, and preferably ≥10⁻⁴ S/cm, and more preferably ≥10⁻³ S/cm. Invarious embodiments the glass stability factor is increased by at least20° C., 30° C., 40° C., 50° C., 60° C., or 70° C. by the oxygenreplacement for sulfur, while maintaining the requisite Li ionconductivity of ≥10⁻⁵ S/cm. In various embodiments the Hruby parameteris increased by at least 0.2, 0.3, 0.4, 0.5, 0.6, or 0.7 by the oxygenreplacement for sulfur or the silicon replacement for boron, whilemaintaining the requisite Li ion conductivity.

In various methods, the step of selecting the glass composition includesdecreasing the amount of Li by an amount sufficient to increase theglass stability factor by at least 10° C. or the Hruby parameter by atleast 0.1, while maintaining a Li ion conductivity ≥10⁻⁵ S/cm, andpreferably ≥10⁻⁴ S/cm, and more preferably ≥10⁻³ S/cm. In variousembodiments the glass stability factor is increased by at least 20° C.,30° C., 40° C., 50° C., 60° C., or 70° C. by the decrease in Li content,while maintaining at least the requisite Li ion conductivity of ≥10⁻⁵S/cm. In various embodiments the Hruby parameter is increased by atleast 0.2, 0.3, 0.4, 0.5, 0.6, or 0.7 by the decrease in Li content,while maintaining the aforesaid Li ion conductivity values.

In various methods, the step of selecting the glass compositionincludes: i) selecting a sulfide base glass system composed of at leastone glass former and glass modifier; ii) determining a high conductivitycomposition within the selected glass system (e.g., the highest Li ionconductivity, or within 50% of that value); and iii) adjusting the highconductivity composition to increase the glass stability factor and/orHruby parameter by at least 10° C. and/or 10% relative to that of thehigh conductivity composition, or enhancing the glass stability factorand/or Hruby parameter by at least 20° C. or 20%, or at least 30° C. or30%, or at least 40° C. or 40%, or at least 50° C. or 50%; and furtherwherein the Li ion conductivity of the selected composition is lowerthan that of the high conductivity composition by as much as 2 fold, 5fold, 10 fold or even 100 fold lower (e.g., between a 2 fold to 10 foldreduction in conductivity, or between a 10 fold to 100 fold reduction).

In various methods, the step of selecting the glass compositionincludes: i) selecting a sulfide based glass system composed of at leastone glass former and glass modifier; ii) determining a high conductivitycomposition within the selected system which has the highest Li ionconductivity (or within 50% of that value); and iii) adjusting the highconductivity composition to increase the glass viscosity at the liquidustemperature by at least 10% relative to the high conductivitycomposition (and preferably by at least 20%, or at least 30%, or atleast 40%, or at least 50%); and further wherein the Li ion conductivityof the selected composition is lower than that of the high conductivitycomposition by as much as 2 fold, 5 fold, 10 fold or even 100 fold(e.g., between 2 fold to 10 fold reduction or between a 10 fold to 100fold reduction in Li ion conductivity).

Continuing with reference to FIGS. 5A-C, once the Li ion conductingsulfur containing glass composition is selected 505, the raw precursormaterials (e.g., Li₂S, SiS₂, and P₂S₅ powders) 510 are processed. Withreference to methods 500A-B, as illustrated in FIGS. 5A-B, theprocessing steps involve forming a vitreous preform 530A from the rawprecursor materials, or melting the raw precursor materials 530B formaking the vitreous solid electrolyte sheet by melt drawing. In method500C the process involves the extra step of making a glass batch 520Cfrom the raw precursor materials, and then processing the glass preformor drawing a sheet from the twice-melted glass. In various embodiments,the batch glass formed in step 520C may be processed by melt/quenchingthe raw material precursors or by mechanical milling. The re-melting orformation of a vitreous preform from a batch glass, regardless of how it(the batch glass) is formed, allows better control of processingvariables, including minimizing loss of volatile constituents.

In various embodiments vitreous solid electrolyte sheet 100 issufficiently flexible and long to be configured as a continuous web ofLi ion conducting glass, typically wound on a spool, and thus suitableas a source roll for downstream (R₂R) or roll-to-sheet processing ofelectrode subassemblies, electrode assemblies and battery cells.Preferably the continuous web has bending radius ≤100 cm, and preferably≤50 cm, more preferably ≤30 cm, even more preferably ≤10 cm, and yeteven more preferably ≤5 cm, or ≤2.5 cm, or ≤1 cm, and thus can be woundas such without fracture.

In various embodiments the spool or drum has a diameter >100 cm and <200cm; or >50 cm and ≤100 cm; or >25 cm and ≤50 cm; or >10 cm and ≤25;or >5 cm and ≤10 cm; or >1 cm and ≤5 cm; or >0.5 cm and ≤1 cm. Invarious embodiments the freestanding and flexible vitreous sulfur-basedglass strip is ultimately wound about a spindle for incorporation into abattery cell, the spindle having a diameter of about 1 cm or less (e.g.,a spindle of diameter 5 mm, 4 mm, 3 mm, 2 mm, 1 mm, and 0.5 mm).

The instant web of vitreous solid electrolyte glass sheet is typicallyof sufficient length for cutting to size solid electrolyte ribbons forat least two individual solid electrolyte separator components orelectrode assembly components. Typically, the length of the web issufficient for making many multiples of such said components (e.g., atleast 5, at least 10, or at least 20 of such said components). Forexample, at least 5, 10 or at least 20 discrete solid electrolyteribbons. For instance, in various embodiments the length of the solidelectrolyte web of vitreous Li ion conducting sulfide glass is more than20 cm, 50 cm, 100 cm, 500 cm or more than 1000 cm long.

Preferably, the vitreous web of solid electrolyte glass is flexible, andformed as a continuous roll on a spool for storage, transportation andcomponent manufacture, such as, in various embodiments, roll to roll(R₂R) manufacturing of downstream battery cell components, includingelectrode subassemblies, electrode assemblies, and battery cellsthereof. Preferably, the solid electrolyte web has sufficiently highsurface quality and thickness uniformity that it requires no postsolidification grinding and/or polishing. In making a solid electrolyteseparator component from the web, discrete solid electrolyte glasssheets of predetermined length and width are cut to size (e.g.,preferably a laser cutting).

In various embodiments, the continuous web of vitreous Li ion conductingglass serves as a downstream substrate onto which a lithiumelectroactive material layer (e.g., lithium metal) or a tie-layer and/ora current collecting layer (e.g., Cu or Ni metal) is deposited or placedwith adherence (i.e., adhered to the vitreous glass web). When makingindividual lithium electrode assemblies from a continuous web, invarious embodiments the lithium metal layer may be deposited or adheredonto the web in an intermittent fashion, and typically in periodicsections, thus creating lithium coated sections separated by uncoatedregions (e.g., by using masking techniques). In other embodiments,individual glass sheets may be cut to size from the vitreous web priorto depositing the lithium metal layer or tie-layer and/or currentcollecting layer.

In various embodiments roll processing of the web is inline with thesolid electrolyte vitreous glass sheet drawing process. With referenceto FIG. 6, there is illustrated a sheet to roll fabrication system 600for processing a vitreous web of solid electrolyte glass 100W in theform of a continuous roll. Sheet to roll fabrication system 600 includessolid electrolyte sheet drawing apparatus 610 (e.g., melt draw orpreform draw apparatus 400 or 400D respectively, such as a fusion drawapparatus, a slot draw apparatus, or a redraw/preform draw apparatus)configured inline with roll processing apparatus that includes one ormore drive mechanisms 623 (e.g., a pair of opposing counter rotatingrollers), guide rollers 628, and take-up spool 626 for winding theinorganic vitreous solid electrolyte glass sheet into continuous roll100R. Preferably, the counter rollers, which are generally motor-driven,are positioned to contact a peripheral edge region of the as-drawn solidelectrolyte sheet, and in this way the major area portion of the solidelectrolyte sheet (e.g., the high quality center portion) is maintainedin a pristine surface state condition (i.e., untouched). Driven by therotating rollers, solid electrolyte ribbon (long sheet) 100W istypically conveyed along one or more guide rollers (e.g., roller 628)before engaging with take-up roll 626. The web of solid electrolyteglass 100W may be conveyed in an unsupported fashion, or the apparatusmay include a support mechanism for supporting the moving vitreous glassribbon as it is conveyed toward the take-up roll, and/or into one ormore processing stages 650 (650 i, 650 ii, 650 iii, 650 iv). Typically,solid electrolyte web 100W is caused to traverse through a furnace orhot zone stage 650 i for annealing the glass sheet prior to engagingwith the take-up roll for winding. The processing stages may include aslitting stage 650 ii with a cutting device (e.g., a wire saw)configured to remove edge portions from the high quality center portionof the as-drawn glass. Other stages are contemplated, including a stagefor configuring a protector element along the lengthwise edges of thesolid electrolyte sheet 650 iii and/or material layer coating stages 650iv for coating the surface of solid electrolyte glass web 100W with atie-layer coating and/or a current collector coating and/or a lithiummetal layer, as described in more detail herein below with respect tomaking a web of electrode sub-assemblies and/or a web of lithiumelectrode assemblies.

Optionally, to keep the solid electrolyte sheet surfaces from directlycontacting each other, interleave 604 (a protective web material layer)may be wound together with the inorganic web of solid electrolyte glassvia interleave supply roll/take off-roll 612. The interleaf interposedbetween layers of the glass sheet roll. Care should be taken in theproper selection of the interleaf, and in particular embodiments themajor opposing surfaces of interleave material layer 604 are composed ofvitreous carbon (e.g., the interleave may be an organic polymer layer(e.g., a polyolefin or polyester layer) or thin inorganic glass having avitreous carbon surface coating). Also contemplated is the use of edgeprotector elements, which, as described above, protect the edges of thesolid electrolyte sheet against physical damage, and may also serve as aspacer between sheet layers when the web is wound on a spool, and inthis way, the high quality center portion of the solid electrolyte sheetis kept in a pristine surface state (i.e., untouched by a foreign solidsurface).

Electrode Sub-Assembly

With reference to FIGS. 7A-B, there is illustrated electrode subassembly700A-B, which, in accordance with the present disclosure, generallyserves as a standalone component for making a lithium metal electrodeassembly, and in some embodiments may be incorporated directly into abattery cell, also of the present disclosure. As illustrated,subassembly 700A-B is a freestanding substrate laminate composed of asolid electrolyte sheet 100 covered in direct contact by material layer1101, which provides a surface for creating an electrochemicallyefficient interface with a lithium metal layer during the making of astandalone lithium metal electrode assembly or during the course ofcharging in a battery cell.

Material layer 701 may be characterized as having interior surface 701 iadjacent to and in direct contact with surface 101A of solid electrolytesheet 100, and exposed surface 701 ii opposing the exterior environmentabout the subassembly. Typically, material layer 701 is significantlythinner than solid electrolyte sheet 100 on which it is coated, formedon or adhered to. In various embodiments material layer 701 or a layerportion thereof is a transient layer that effectively disappears (e.g.,by alloying) once a lithium metal layer is applied or deposited onto it.

As mentioned above, electrode subassembly 700A-B is a standalonecomponent useful for making a lithium metal electrode assembly orbattery cell of the present disclosure. However, the electrodesubassembly by itself is not a capacity-bearing electrode, and thus doesnot contain electroactive material (e.g., Li metal) for providingampere-hour capacity to a battery cell. Accordingly, electrodesubassembly 700A-B has exceptional component shelf life andhandle-ability for manufacturing.

With reference to FIG. 7A, in various embodiments electrode subassembly700A is a bi-layer laminate of material layer 701 (a single layer,typically of uniform composition) coated, adhered or placed onto solidelectrolyte sheet 100. With reference to FIG. 7B, in variousembodiments, subassembly 700B is composed of more than two layers; forinstance, material layer 701 may itself be a multilayer of two or morematerial layers disposed on surface 101A of sheet 100 (e.g., 701 a atie-layer in direct contact with solid electrolyte sheet 100, and secondlayer 710 b a current collector layer in direct contact with thetie-layer).

In various embodiments material layer 701 is a chemically functionaltie-layer coating for creating an electrochemically efficient interfacebetween sheet 100 and a lithium metal layer, and may also provide someprotection against damage during storage and handling. Accordingly, thetie layer is of suitable composition and thickness to enhance bonding.In particular embodiments the tie-layer reactively alloys with Li metalon contact to form an electrochemically operable interface. Thetie-layer is preferably a transient layer, which transforms andessentially disappears upon the formation or deposition of lithium metalon its surface. In various embodiments the tie-layer is thin enoughand/or the lithium layer is of sufficient mass (i.e., thickness) tocompletely dissolve the tie layer (e.g., via an alloying reaction), andpreferably the elements of the tie-layer are in such small amount andfully dispersed throughout the lithium metal layer to be insignificant.

In various embodiments protective tie-layer 701 is a coating of a metalor semi-metal suitable for forming an electrochemically operableinterface between a lithium metal layer and solid electrolyte sheet 100,and, in particular, an electrochemically efficient interface for platingand striping lithium metal in a battery cell. In various embodiments,the tie-layer is a metal or semi-metal such as Al, Ag, In, Au, Sn, Si,or the like, or an alloy or inter-metallic combination of metals orsemi-metals capable of alloying or being alloyed by lithium metal oncontact.

In various embodiments the tie-layer 701 is a metal or semi-metalcoating deposited by physical vapor deposition (e.g., by evaporation)onto first principal side surface 101A of sheet 100. Tie-layer 701 is atransient film that on contact with Li metal atomically dispersesthroughout the lithium metal layer. In various embodiments tie-layer 701is of a composition and thickness to fully alloy with lithium metal oncontact at room temperature, and in some embodiments heat may be appliedto facilitate alloying and atomic diffusion. In various embodiments thetie-layer thickness is in the range of 0.05 to 5 μm and more typicallybetween 0.05 to 1 μm (e.g., about 0.05 μm, or 0.1 μm, 0.2 μm, 0.3 μm,0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, or about 1.0 μm, or 2.0μm, 3.0 μm, 4.0 μm or about 5.0 μm).

The tie-layer provides a subassembly surface for mating the solidelectrolyte sheet to a lithium metal layer (e.g., extruded lithiumfilm), when forming a lithium electrode assembly or battery cell of thepresent disclosure. In particular, by reactively alloying with Li metal,the tie layer facilitates formation of an electrochemically operableinterface. Moreover, the tie-layer is a transient material layer in thatonce the lithium metal layer is applied or formed, the tie-layereffectively disappears as it alloys with Li.

With reference to FIG. 7A, in various embodiments the lithium metallayer is applied onto exterior tie-layer surface 701 ii duringfabrication of a lithium electrode assembly (e.g., a Li foil hot rolledonto the tie-layer). In other embodiments the lithium metal layer isformed by electrochemically plating Li metal adjacent to interiortie-layer surface 701 i during initial charging of a battery cell inwhich the electrode subassembly is incorporated. Whether formedelectrochemically in a battery cell or applied or coated to form alithium metal electrode assembly, lithium metal interacts with thetie-layer to form an intimate electrochemically operable interfacebetween the as-formed or applied lithium metal layer and first principalside surface 101A of solid electrolyte sheet 100.

With reference to subassembly 700B in FIG. 7B, in various embodimentsmaterial layer 701 is a multilayer (e.g., a bi-layer) devoid of Limetal. In various embodiments bi-layer 701 is composed of tie-layer 701a in direct contact with first principal side surface 101A of sheet 100,and current collecting layer 701 b in direct contact with the tie-layer.The tie-layer sandwiched between sheet 100 and current collecting layer701 b. In various embodiments the tie-layer may be evaporated onto thesolid electrolyte sheet 100 followed by applying a current collectinglayer 701 b directly onto the tie-layer 701 a. In other embodiments itis contemplated that the tie-layer may be evaporated onto the currentcollector layer, and the multi-layer, so formed, applied onto the sheet.Multiple tie-layer coatings are also contemplated herein, such as one ormore additional tie-layer coatings disposed between tie-layer 701 a andcurrent collecting layer 701 b. For instance, an additional tie-layermay be utilized to enhance and improve the Li metal interface in directcontact with current collecting layer 701 b.

In alternative embodiments it is contemplated that the currentcollecting layer may be applied directly onto sheet surface 101A, in theabsence of a tie-layer.

The current collector layer may be a thin metal foil, or a thin metalfilm on a polymer substrate, or a coating applied directly onto sheetsurface 101A, or indirectly via a tie-layer. For example a thin Cu or Nifoil, or a laminate of a Cu film on a polyethylene terephthalate (PET)substrate. The current collector should be a material layer that issubstantially unreactive in contact with Li metal and of sufficientelectronic conductivity to provide effective current collection,typically a metal (e.g., Cu or Ni).

In various embodiments, the current collecting layer is preferablysignificantly thinner than solid electrolyte sheet 100 (e.g., ≤⅕ or ≤1/10 the thickness of sheet 100), and preferably no thicker than 10 μm.In various embodiments the current collecting material layer is <20 μmthick, and typically <15 μm, and more preferably ≤10 um, and even morepreferably ≤5 μm thick (e.g., between 10 to 5 μm thick; for exampleabout 5 μm, or 4 μm, or 3 μm, or 2 μm, or 1 μm thick).

In various embodiments, electrode subassembly 700A serves as a substratecomponent for making a standalone lithium metal electrode assembly ofthe present disclosure. In other embodiments electrode subassembly 700Amay be directly incorporated into a lithium battery cell as a lithiumfree negative electrode, completely devoid of Li metal, as described inmore detail below.

Electrode Assembly

With reference to FIG. 8A, standalone electrode assembly 800A is alithium metal electrode assembly composed of solid electrolyte sheet 100serving as a substrate for lithium metal component layer 820, which iscomposed of lithium metal layer 810 and optional current collectinglayer 812. By use of the term standalone with respect to the lithiummetal electrode assembly it is meant that the electrode assembly is adiscrete component absent of a positive electrode and that it exists asa freestanding component outside of a battery cell.

In various embodiments, standalone lithium metal electrode assembly 800contains sufficient amount of Li metal to support the rated capacity ofthe cell in which it is disposed, and in particular matches or exceedsthe rated area ampere-hour capacity of the positive electrode. Forexample, the positive electrode having an area capacity of 1 mAh/cm² andthe Li metal layer thickness is at least 5 μm; or 1.5 mAh/cm² and the Limetal layer thickness is at least 7.5 μm; or 2 mAh/cm² and the Li metallayer thickness is at least 10 μm; or 2.5 mAh/cm² and the Li metal layerthickness is at least 12.5 μm; or 3 mAh/cm² and the Li metal layerthickness is at least 15 μm; or 3.5 mAh/cm² and the Li metal layerthickness is at least 17.5 μm; or 4 mAh/cm² and the Li metal layerthickness is at least 20 μm; or 4.5 mAh/cm² and the Li metal layerthickness is at least 22.5 μm; or 5 mAh/cm² and the Li metal layerthickness is at least 25 μm.

In other embodiments, the amount of lithium metal in standaloneelectrode assembly 800, prior to incorporation into a battery cell, isinsufficient to support the rated capacity of the cell. For instance,the rated capacity of the cell is about 50% greater than the Li metalcapacity of the standalone electrode assembly, or about 100% greater, orabout 150% greater, or about 200% greater, or about 250% greater, orabout 300% greater, or about 350% greater, or about 400% greater, orabout 450% greater, or about 500% greater. For example, the positiveelectrode having an area capacity of 1 mAh/cm² and the Li metal layerthickness is <5 μm; or the positive electrode having an area capacity of2 mAh/cm² or about 3 mAh/cm² or about 4 mAh/cm² or about 5 mAh/cm² andthe Li metal layer thickness is <10 μm (e.g., about 5 μm).

In some embodiments electrode assembly 800 is fabricated by depositinglithium metal layer 810 (e.g., by evaporation or sputter deposition)directly onto sheet surface 101A or indirectly via a tie-layer (e.g.,the lithium deposited onto exterior surface 701 ii of subassembly 700A,as illustrated in FIG. 7A). When evaporated, lithium metal layer 810typically has thickness in the range of 5 to 30 μm (e.g., about 5 μm,about 10 μm, about 15 μm, about 20 μm, about 25 μm, or about 30 μm.

In other embodiments, the Li metal layer may be an extruded Li foil, orLi film on a current collecting substrate, with the thickness of thelithium metal layer being about 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm,35 μm, 40 μm, 45 μm, or 50 μm thick). Electrode assembly 800 formed byadhering the Li foil or Li film directly onto surface 101A of solidelectrolyte sheet 100 (e.g., by laminating with heat) or by laminatingthe Li foil/film to a subassembly of a tie-layer coated sheet, asdescribed above. To enhance bonding and improve the interface, the Lifoil/film is treated or processed to expose fresh Li surfaces just priorto lamination. For example, in various embodiments the Li foil isfreshly extruded and then immediately laminated to sheet 100, or the Lifoil/film may be treated to expose fresh surfaces (e.g., by bristlescrubbing the surface). The freshly extruded or treated foil is thenimmediately mated to sheet 100 (e.g., directly onto sulfide glasssurface 101A or a tie layer if a subassembly is employed). Exposure ofthe fresh Li surfaces to the ambient environment should be minimized tothe maximum possible extent, and the ambient environment should have avery low moisture and oxygen content of preferably less than 10 ppm.

By use of the term “fresh” when referring to an extruded Li foil or afreshly scrubbed lithium metal surface it is meant that the ambientexposure time between extruding/scrubbing and laminating is limited toavoid forming a prohibitively thick resistive film on the lithiumsurface. To be considered fresh, ambient exposure should be limited tominutes, typically <10 minutes, and preferably <1 minute and morepreferably <30 seconds. In embodiments, ambient exposure is between 1-3minutes, or less than 60 seconds, or less than 30 seconds, or less than20 seconds, or less than 10 seconds (e.g., within about 10 or 5seconds).

With reference to FIG. 8B, in other embodiments standalone lithium metalelectrode assembly 800 may be formed by laminating current collectinglayer 812 directly onto solid electrolyte sheet 100 by evaporating Limetal or by spraying molten lithium as a bonding layer between it (812)and sheet 100, followed by optional roller pressing. Notably, prior tothe laminating step, current collector 812 (e.g., Cu foil) is devoid ofLi metal, and thus the technique provides a method for bonding sheet 100to a discrete self-supporting Cu foil in the absence of a pre-existinglithium metal layer. Moreover, the thickness of the Li metal bondinglayer can be adjusted. In various embodiments it is advantageous to havean exceptionally thin bonding layer, of thickness sufficient to effectbonding but otherwise scant as it pertains to the amount of capacity itprovides to a battery cell. For example, a scant Li metal bonding layermay have thickness of no more than about 5 μm (e.g., about 1-2 μm), andis highly advantageous when combining the electrode assembly with a Liion positive electrode in a battery cell, wherein almost all of the Licell capacity is derived from the fully lithiated intercalation compoundof the positive electrode (e.g., LCO, NCA, NMC). In operation, the thinLi metal bonding layer serves as a seed layer for enhancing uniformityof Li metal deposition onto current collector 812 during initialcharging of the battery cell, without burdening the cell with anovercapacity of Li metal because it (the bonding layer) is scantrelative to the area capacity of the positive electrode.

In an alternative embodiment, not shown, it is contemplated that currentcollector layer 812 may have a pre-existing lithium metal layer alreadypresent on its surface prior to laminating to the solid electrolyte inthe presence of a lithium metal vapor.

With reference to FIG. 8C there is illustrated what is termed herein anencapsulated standalone lithium metal electrode assembly 800C. Invarious embodiments encapsulated assembly 800C is composed of lithiummetal component layer 820 encapsulated between a first solid electrolytesheet 100 and an opposing backplane component 830 impermeable to liquidsit comes into contact with, and preferably non-reactive. Lithium metalcomponent layer 820 comprises a lithium metal layer in direct contactwith sheet 100, and one or more optional layers, as described in moredetail below, which are adjacent to backplane 830. Solid electrolytesheet 100 and backplane component 830 respectively define the majorexterior opposing surfaces of the lithium metal electrode assembly. Byuse of the term encapsulate when referring to the lithium metalcomponent layer of the assembly it is meant that the solid electrolytesheet and backplane component are in contiguous mechanical force contactwith the lithium metal component layer. Accordingly, as a result of theencapsulation, lithium metal component layer 820, and in particular thelithium metal layer, may be subjected to stacking pressure whenincorporated in a battery cell.

In some embodiments the encapsulated lithium metal electrode assembly isdouble-sided and the backplane component is a second solid electrolytesheet (e.g., substantially identical to the first solid electrolytesheet). In other embodiments, backplane component is not a Li ionconductor, and the encapsulated lithium metal electrode assembly isreferred to herein as single-sided; for instance, the backplane may be asubstantially inert material layer or an electronically conductivematerial layer with current collector functionality. By use of the termsingle-sided or double-sided it is meant with respect to whether one orboth sides of the electrode assembly supports Li ion through transport(via electrical migration).

With reference to FIG. 8D, in some embodiments encapsulated electrodeassembly 800D is double-sided, and the backplane component is a secondsolid electrolyte sheet (designated as 100-2). When double-sided,lithium metal component layer 820 is typically a tri-layer composed ofcurrent collecting layer 812 disposed between first and second lithiummetal layers, 810-1 and 810-2 respectively.

In various embodiments, the encapsulated double-sided lithium metalelectrode assembly is fabricated by providing a first and a secondlithium metal electrode assembly as described above with reference toFIG. 8A, and combining the two assemblies between a single currentcollecting layer 812, or when the two assemblies are provided each withtheir own current collecting layer, they may be combined by placing oneon the other (i.e., current collector to current collector).

With reference to FIG. 8E, in other embodiments, the backplane componentis not a Li ion conductor, and assembly 800E, encapsulated, issingle-sided. In various embodiments, when single-sided, backplanecomponent 830 may be an inert material component layer, orelectronically conductive with current collector functionality. Forinstance, inert backplane component 830 may be a polymeric layer (rigidor flexible) or when electronically conductive, the backplane may be amulti-layer of at least one polymer layer providing an exterior surfaceof the assembly and an electronically conductive metal layer inelectronic communication with the lithium metal layer (e.g., in directcontact with the lithium metal layer or in direct contact with a Cucurrent collecting layer).

In various embodiments the encapsulated assembly may be edge sealedalong the lengthwise and/or widthwise dimensions. When entirely sealedalong its edges, the assembly is fully sealed and preferably hermetic,and the lithium metal layer(s) are isolated from the externalenvironment.

With reference to FIG. 8F, in various embodiments the edge seals (e.g.,lengthwise edges as shown) may be effected by fusion or pinch sealingthe peripheral edges of solid electrolyte sheet 100-1 to that of solidelectrolyte sheet 100-2. The direct bonding between sheets 100-1 and100-2 may be performed with heat and/or pressure. For instance byheating the periphery of one or both sheets above T_(g) (e.g., using alaser to heat the edges), and more typically above the softeningtemperature, and pressing/compressing (i.e., pinching) to effect theseal, or heating above T_(m) and allowing the sheets to fusion seal toeach other.

In other embodiments, as shown in FIG. 8G, the edge seal(s) may includea discrete sidewall component 835 interfacing with solid electrolytesheet 100-1 and backplane component 830. The discrete sidewall componentmay be an inert polymer or a glass wire placed along the lengthwise edgeand then heat/fusion sealed to sheet 100 and the backplane component 830(e.g., a second solid electrolyte sheet). When the edge seal is madewith a fusion sealable glass, it is generally not a Li ion conductor(e.g., a non-conducting sulfide glass). In other embodiments thediscrete sidewall component may be an epoxy seal; e.g., the epoxyapplied as a viscous fluid along the lengthwise edge(s), and then cured(e.g., with heat).

Positive Electrode Assembly

With reference to FIG. 9, in various embodiments the electrode assemblyis a standalone positive electrode assembly, wherein a positiveelectroactive component layer is encapsulated between a pair of vitreoussolid electrolyte sheets of the present disclosure. Specifically,positive electrode assembly 900 is double-sided and composed of firstand second solid electrolyte sheets 100-1 and 100-2 edge sealed viadiscrete sidewall component 895 (e.g., as described above in variousembodiments for the lithium metal electrode assemblies). Positiveelectroactive material component layer 960 is typically a tri-layer ofcurrent collecting layer 964 (e.g., aluminum or stainless foil) coatedon both sides by an electroactive material layer 962-1 and 962-2, which,in various embodiments has a lithium ion intercalation compound as itselectroactive material (e.g., an oxide such as e.g., LiCoO₂, LiMn₂O₄,LiNiO, LiNi_(0.33)Mn_(0.33)Co_(0.33)O₂, LiNi_(0.8)Co_(0.15)Al_(0.05)O₂).In various embodiments, positive electrode assembly 900 includes liquidelectrolyte in contact with electroactive layer 962, and present in itspores. In various embodiments, as shown, the assembly includes a firstand second porous separator layer or gel electrolyte layer (designatedas 970-1 and 970-2, respectively), which, impregnated with liquidelectrolyte, provide positive separation between the electroactivelayers and their opposing solid electrolyte sheets. Preferably theassembly is well sealed around its edges, and the liquid electrolyte isprevented from seeping out (e.g., hermetically sealed). In alternativeembodiments the positive electrode assembly may be single-sided andsecond solid electrolyte sheet 100-2 replaced with a backplane componentimpermeable to the liquid electrolyte and preferably non-reactive (e.g.,a polymer or metal layer). When double-sided, it is contemplated thatpositive electrode assembly 900 may be edge sealed with a fusion orpinch seal as described above, rather than using a discrete sidewallcomponent. In some embodiments, a solid polymer electrolyte may be usedto effect positive separation between the electroactive layers and theopposing solid electrolyte sheets. In this way, the positive electrodeassembly may be devoid of a liquid electrolyte.

Battery Cells

With reference to FIG. 10A there is illustrated a lithium battery cell1000A in accordance with the present disclosure, the battery cellcomprising a cell laminate 1001 including solid electrolyte sheet 100disposed between positive electrode 1060 and negative lithiumelectroactive layer 1010, for example a lithium metal layer such asthose described above with reference to layer 810 in FIGS. 8A-I.

In various embodiments the combination of lithium electroactive layer1010 (e.g., an evaporated or extruded lithium metal layer) and solidelectrolyte sheet 100 (e.g., a vitreous sulfide glass) is incorporatedin the battery cell as standalone solid-state lithium metal electrodeassembly 800, as described above with reference to FIGS. 8A-I.

Cell laminate 1001 is generally disposed in a cell housing (not shown).In various embodiments the cell laminate is sufficiently flexible to befoldable and more preferably windable, and thereby cell 1000A may be ofa wound prismatic or wound cylindrical construction, or a foldableconstruct disposed in a rigid or pouch-like housing (e.g., a multilayerlaminate material). Battery cell 1000A may be made by: i) combininglayers: 1610, 100, and 1060, to form laminate 1001; ii) winding orfolding the laminate into a shaped construct (e.g., cylindrical orprismatic); iii) placing the shaped construct into a rigid or flexiblehousing such as a multilayer laminate pouch or rigid container; and thensealing the pouch or container. When a liquid electrolyte is employed inthe cell, it is typically dispensed after the laminate is disposed inthe cell housing.

In various embodiments, laminate 1001 is wound or folded with radius ofcurvature ≤3 cm, or ≤2 cm, or ≤1 cm, or ≤0.5 cm, or ≤0.25 cm, withoutfracturing solid electrolyte sheet 100. In various embodiments cell1000A includes a spindle about which laminate 1001 is wound, the spindletypically having diameter ≤6 cm, ≤4 cm, ≤2 cm, ≤1 cm, or ≤0.5 cm.

In various embodiments, positive electrode 1060 includes positiveelectroactive layer 1062 disposed on current collecting layer 1064(e.g., a metal foil, such as aluminum, nickel, stainless steel or thelike). In various embodiments positive electrode 1060 may be solid-state(i.e., devoid of a liquid electrolyte) or it may contain a liquidelectrolyte, typically impregnated in the pores of electroactive layer1062. In various embodiments positive electroactive layer 1062 is alithium ion intercalation layer composed of a lithium ion intercalationcompound as the electroactive material. When combined with a liquidelectrolyte, positive electroactive layer 1662 is typically porous, andwhen solid-state the layer is preferably dense (e.g., a highly compactedparticle composite). Particularly suitable lithium ion intercalationcompounds include, for example, intercalating transition metal oxidessuch as lithium cobalt oxides, lithium manganese oxides, lithium nickeloxides, lithium nickel manganese cobalt oxides, lithium nickel cobaltaluminum oxides (e.g., LiCoO₂, LiMn₂O₄, LiNiO,LiNi_(0.33)Mn_(0.33)Co_(0.33)O₂, LiNi_(0.8)Co_(0.15)Al_(0.05)O₂ and thelike) or intercalating transition metal phosphates and sulfates (e.g.,LiFePO₄, Li₃V₂(PO₄)₃, LiCoPO4, LiMnPO₄, and LiFeSO₄) or others (e.g.,LiFeSO₄F and LiVPO₄F), as well as high voltage intercalating materialscapable of achieving cell voltages versus lithium metal in excess of 4.5Volts.

In various embodiments the electroactive material of layer 1062 is ofthe conversion reaction type including transition metal oxides,transition metal fluorides, transition metal sulfides, transition metalnitrides and combinations thereof (e.g., MnO₂, Mn₂O₃, MnO, Fe₂O₃, Fe₃O₄,FeO, Co₃O₄, CoO, NiO, CuO, Cu₂O, MoO₃, MoO₂, and RuO₂)).

In various embodiments the electroactive material of layer 1062 iselemental sulfur and/or lithium polysulfide species, typically dissolvedin a non-aqueous liquid electrolyte. In such said embodiments, thebattery cell may be considered a lithium sulfur battery. Generally, whenmaking use of dissolved electroactive species (polysulfides orotherwise), electroactive layer 1062 is an electron transfer medium thatfacilitates electrochemical redox during discharge and charge, and, assuch, is typically a porous metal or porous carbonaceous layer.

In various embodiments battery cell 1000A is of the hybrid cell type,having a fully solid-state negative electrode (e.g., a fully solid-statelithium metal electrode assembly) and a positive electrode impregnatedwith a liquid electrolyte, and thus the positive electrode notsolid-state. In other embodiments cell 1000A is fully solid-state, andthus entirely devoid of liquid phase electrolyte. In various fully solidstate cell embodiments, solid electrolyte sheet 100 serves as the solesolid electrolyte separator layer between negative lithium electroactivelayer 1010 (e.g., a lithium metal layer) and positive electrode 1060.

In various embodiments cell 1000A is not fully solid state, and thusincludes a liquid phase electrolyte. In some embodiments the liquidphase electrolyte is a common electrolyte present throughout the celland contacts both the positive electrode (e.g., positive electroactivelayer 1062) and negative lithium electroactive layer 1010 (e.g., lithiummetal layer). By use of the term “common electrolyte” it is meant thatthe liquid electrolyte contacts both the negative electroactive layerand the positive electroactive layer, and thus the “common liquidelectrolyte” is continuous throughout cell laminate 1001. A commonliquid electrolyte yields a rather unusual and counterintuitive cellconstruction, in that it employs both a solid-state separator composedof solid electrolyte sheet 100 (preferably devoid of through porosity)and a continuous liquid phase electrolyte that contacts both positiveelectroactive layer 1062 and negative electroactive layer 1010. In fact,solid electrolyte sheet 100 may be used as a Li ion conducting solidelectrolyte separator layer in an otherwise conventional lithium ioncell, with the solid electrolyte sheet providing through conduction forLi ions while preventing short circuiting by lithium dendrites andproviding protection against thermal runaway. In some embodiments, sheet100 serves as a direct replacement for the micro-porous polymericseparator layer commonly employed in conventional lithium ion cells(e.g., Celgard® or the like), and in such embodiments battery cell 1000Aincludes a common liquid electrolyte but is explicitly devoid of aporous separator layer. For example, battery cell 1000A may be embodiedby positive electrode 1060 having porous positive electroactive layer1062 comprising a lithium ion intercalation compound (e.g., LiCoO₂) andporous negative electroactive layer 1010 having as its electroactivematerial a lithium ion intercalation material or alloying material(e.g., intercalatable carbon or silicon or some combination thereof).Moreover, while this disclosure contemplates that the common liquidelectrolyte may exist primarily in the pores of the positive andnegative electroactive layers, it is not limited as such, and in someembodiments the cell may include one or more porous separator layers(e.g., a micro-porous polymer layer such as a porous polyolefin or thelike) or gel electrolyte layer positioned between solid electrolytesheet 100 and electroactive layer(s) 1010 and/or 1062. When incorporatedin a cell having a common liquid electrolyte, solid electrolyte sheet100 is preferably substantially impervious to the common liquidelectrolyte, but the invention is not necessarily so limited.

In various embodiments the battery cell of the present disclosure is ofa hybrid cell type: composed of a solid-state and sealed negativeelectrode assembly, as described above, and a positive electrodeimpregnated with a liquid electrolyte. When referring to an electrodeassembly as solid-state it is meant that the assembly does not containliquid, and in particular that the electroactive material of theassembly does not contact liquid phase electrolyte.

With reference to FIG. 10B, in various embodiments battery cell 1000B isof the hybrid type, and solid-state negative electrode assembly 1040 isan edge sealed lithium metal electrode assembly, such as 800H,illustrated in FIG. 8H. In particular embodiments the liquid electrolyteis present in the pores of positive electroactive material layer 1062,and is chemically compatible in direct contact with second side surface101B of sheet 100. To prevent the liquid electrolyte from contactinglithium metal layer 810, solid electrolyte sheet 100 should be free ofthrough porosity and impermeable to the liquid electrolyte, andtherefore substantially impervious.

In various embodiments, and in particular when the solid electrolytesheet is a sulfide based glass, the liquid phase electrolyte isnon-aqueous, and exceptionally dry, meaning that it is has very lowmoisture content, preferably less than 20 ppm, more preferably less than10 ppm, and even more preferably less than 5 ppm. Non-aqueous liquidelectrolytes suitable for use herein include solutions of organicsolvent(s), such as carbonates (e.g., DMC, EEC, PC, EC), and a lithiumsalt dissolved therein (e.g., LiBF₄, LiClO₄, LiPF₆, LiTf and LiTFSI;where Tf=trifluormethansulfonate;TFSI=bis(trifluoromethanesulfonyl)imide), as well as liquid electrolytesbased on ionic liquids, as are known in the battery field arts.

In various embodiments, cell laminate 1001B includes separator layer1070 disposed between negative electrode 1040 and positive electrode1060; the separator layer typically a porous material layer or gelelectrolyte layer impregnated with the non-aqueous liquid electrolyte.For instance, separator layer 1070 a porous organic polymer, such as aporous polyolefin layer (e.g., microporous). Separator layer 1070provides positive separation between second principal side surface 101Bof solid electrolyte sheet 100 and positive electroactive material layer1062. The separator layer may provide various benefits. In particularembodiments, layer 1070 enables the combination of a solid electrolytesheet and a positive electroactive material layer that are chemicallyincompatible in direct contact with each other. In other hybrid cellembodiments, the composition of solid electrolyte sheet 100 ischemically compatible in direct contact with the positive electroactivematerial of layer 1062, and laminate 1001B may be absent layer 1070, andsheet 100 and layer 1062 disposed in direct contact. Cell laminate 1001Bmay be wound or folded and incorporated into a cell housing. Thereafter,the liquid phase electrolyte dispensed into the cell, wherein itcontacts positive electrode 1020B but does not contact lithium metallayer 810, as it is isolated inside the sealed electrode assembly.

In particular embodiments cell 1000B is composed of: i) electroactivelayer 810—a lithium metal layer; ii) solid electrolyte sheet 100—asubstantially impervious vitreous Li ion conducting sulfide based glasssheet; iii) positive electroactive material layer 1062—composed of alithium intercalation material, such as an oxide (e.g., LiCoO₂, LiMn₂O₄,LiNiO, LiNiMnCoO₂ or the like) or phosphate (e.g., LiFePO₄); iv)optional separator layer 1670—a porous polymer or gel, impregnated witha liquid phase electrolyte; v) a non-aqueous liquid phase electrolytepresent in the pores of layers 1062 and 1070, and chemically compatiblewith second principal side surface 101B of sulfide based solidelectrolyte glass sheet 100. For instance, lithium metal layer 810 andsolid electrolyte sheet 100 incorporated into cell 1000B as an edgesealed solid-state lithium metal electrode assembly.

With reference to FIG. 10C there is illustrated a fully solid-statebattery cell 1000C in accordance with various embodiments of thisdisclosure. The cell includes solid-state positive electrode 1060C;solid-state negative electrode 1040C; and Li ion-conducting solidelectrolyte sheet 100 serving as separator. In some embodiments,components 1060C/1040C/100 are incorporated into the cell as discretematerial layers. In other embodiments, separator sheet 100 andnegative/positive electrodes 1040C/1060C are incorporated in the cell asstandalone components (e.g., standalone lithium negative electrodeassembly or as a standalone lithium positive electrode assembly.

Solid-state positive electrode 1040C includes positive electroactivelayer 1062C and current collector layer 1024C. In various embodimentselectroactive layer 1062C is a composite of positive electroactivematerial combined with solid electrolyte material of composition similarto, or the same as, that of vitreous sulfide glass sheet 100. Withoutlimitation, particle composite layer 1062 may be fabricated bycompaction or tape casting of positive electroactive particles, Li ionconducting sulfide glass or sulfide glass-ceramic particles, andoptionally electronically conductive particles for enhancing electronicconductivity, such as a carbonaceous material, (e.g., carbon blackparticles). In particular embodiments the positive electroactiveparticles are Li ion intercalating compounds, as described above (e.g.,metal oxides).

Solid-state negative electrode 1040C is composed of electroactivematerial layer 1010C, which may be a lithium metal layer as describedabove, with optional current collecting layer 1012C. In variousembodiments, lithium metal layer 1010C and solid electrolyte sheet 100are incorporated into cell 1000C as a standalone lithium metal electrodeassembly in accordance with various embodiments of the presentdisclosure. In alternative embodiments, negative electroactive layer1010C is not a lithium metal layer, but rather a layer comprisinglithium electroactive material having a potential near that of lithiummetal, such as, but not limited to, intercalatable carbon, silicon or acombination thereof. In such said embodiments, electroactive layer 1010Cmay be a particle compact or tape cast layer of negative electroactivematerial particles (e.g., intercalatable carbon) combined with solidelectrolyte particles of composition similar to, or the same as, thatwhich constitutes sheet 100. Negative electroactive layer 1010C mayfurther contain electronically conductive diluents (such as high surfacearea carbons) as well as binder materials for enhancing mechanicalintegrity of the layer.

In various embodiments fully solid-state battery cell 1000C is composedof positive and negative electrodes that are each composite powdercompacts or tape cast layers, separated by a solid electrolyte sheet ofthe present disclosure (e.g., a vitreous sheet of a Li ion conductingsulfide based glass).

With reference to FIG. 10D there is illustrated a process for making alithium metal battery cell 1000D that, in its as-fabricated state, isdevoid of lithium metal. The cell is composed of cell laminate 1001Dcomprising: i) electrode subassembly 700B having current collectinglayer 701 b and optional tie layer 1101 a, as described above withreference to FIG. 7B; and ii) positive electrode 1060 comprisingelectroactive layer 1062 and current collecting layer 1664. In someembodiments cell 1000D is a hybrid cell with a liquid electrolyteimpregnated as described above with reference to FIG. 10B. In otherembodiments cell 1000D may be a solid-state battery cell, and thereforeabsent liquid electrolyte and its associated separator layer 1070.Continuing with reference to FIG. 10D, electroactive layer 1062 is afully lithiated lithium intercalation material layer, and is the solesource of Li in the as-fabricated cell. Lithium metal 810 is formed as aresult of the initial cell charge, as Li from layer 1062 is plated ontoelectrode subassembly 700B, and in particular onto current collectinglayer 701 b, thereby producing lithium metal component layer 1020.

Finally, with reference to FIG. 10E there is illustrated a lithium metalbattery cell in accordance with the present disclosure; the cell iscomposed of positive electrode assembly 900 (shown in detail in FIG. 9)and lithium metal layer 810-1 and 810-2 disposed in direct contact withfirst surface 101A of respective solid electrolyte sheets 100-1 and100-2.

It is understood that the examples and embodiments described herein arefor illustrative purposes only and that various modifications or changesin light thereof will be suggested to persons skilled in the art.Although various details have been omitted for clarity's sake, variousdesign alternatives may be implemented. Therefore, the present examplesare to be considered as illustrative and not restrictive, and thedisclosure is not to be limited to the details given herein, but may bemodified within the scope of the appended claims.

What is claimed is:
 1. A standalone lithium ion-conductive solidelectrolyte, comprising: a freestanding inorganic vitreous sheet ofsulfide-based lithium ion conducting glass having, a liquid-likesurface; an area of at least 10 cm²; a thickness of no more than 100 μm;and a room temperature intrinsic lithium ion conductivity of at least10⁻⁵ S/cm.
 2. The electrolyte of claim 1, wherein the glass sheet has asubstantially uniform thickness of no more than 100 μm.
 3. Theelectrolyte of claim 1, wherein the glass sheet further comprisessubstantially parallel lengthwise edges.
 4. The electrolyte of claim 1,wherein the glass sheet is a continuous web at least 100 cm in length.5. The electrolyte of claim 1, wherein the glass sheet is a continuousweb at least 1000 cm in length.
 6. The electrolyte of claim 1, whereinthe vitreous sulfide-based glass sheet is characterized as having athreshold current for Li dendrite initiation that is greater than 1mA/cm².
 7. The electrolyte of claim 1, wherein the liquid-like surfacelacks surface flaws having a depth dimension greater than 1% of thesheet thickness.
 8. The electrolyte of claim 1, wherein the sheet lacksof powder particles, inter-particle boundaries, or contiguous voidsextending between first and second principal surfaces that aresufficient to propagate a Li dendrite, and the liquid-like surface lacksflaw manifestations of a pressed powder compact that are sufficient toinitiate Li dendrite penetration.
 9. The electrolyte of claim 1, whereinthe sulfide glass has a glass stability factor {Tx−Tg}<100° C.
 10. Theelectrolyte of claim 1, wherein the sulfide glass has a glass stabilityfactor {Tx−Tg}<50° C.
 11. The electrolyte of claim 1, wherein thesulfide glass has a glass stability factor {Tx−Tg}<30° C.
 12. Theelectrolyte of claim 1, wherein the sulfide-based glass is of a typeLi2S—YSn; Li2S—YSn—YOn and combinations thereof, wherein Y is selectedfrom the group consisting of Ge, Si, As, B, or P, and n=2, 3/2 or 5/2.13. The electrolyte of claim 12, wherein the glass is chemically andelectrochemically compatible in contact with lithium metal.
 14. Theelectrolyte of claim 12, wherein the glass is devoid of phosphorous. 15.The electrolyte of claim 1, wherein the glass comprises Li₂S and/or Li₂Oas a glass modifier and one or more of a glass former selected from thegroup consisting of P₂S₅, P₂O₅, SiS₂, SiO₂, B₂S₃ and B₂O₃.
 16. Theelectrolyte of claim 1, wherein the electrolyte is disposed in a batterycell component as a separator adjacent a negative lithium electroactivelayer.
 17. The electrolyte of claim 1, wherein the electrolyte isdisposed in a battery cell as a separator between a positive electrodeand a negative lithium electroactive layer.
 18. A method of making astandalone Li-ion conductive solid electrolyte, the method comprisingdrawing a molten sheet of Li ion conducting sulfide glass into afreestanding inorganic vitreous sheet of sulfide-based lithium ionconducting glass.
 19. The method of claim 18, wherein the sulfide glasshas a glass stability factor {Tx−Tg}<100° C.
 20. The method of claim 18,wherein the drawn freestanding inorganic vitreous sheet of sulfide-basedlithium ion conducting glass has, a liquid-like surface; an area of atleast 10 cm²; a thickness of no more than 100 μm; and a room temperatureintrinsic lithium ion conductivity of at least 10-5 S/cm.
 21. A methodof making a standalone Li-ion conductive solid electrolyte, the methodcomprising: providing a Li ion conducting sulfide glass pre-form; andpulling on the preform at a temperature sufficient to draw the pre-formto a vitreous glass ribbon having a thickness in the range of 5 μm to100 μm.
 22. The method of claim 21, wherein the sulfide glass has aglass stability factor {Tx−Tg}<100° C.
 23. The method of claim 21,wherein the ribbon is a freestanding inorganic vitreous sheet ofsulfide-based lithium ion conducting glass having, a liquid-likesurface; an area of at least 10 cm²; a thickness of no more than 100 μm;and a room temperature intrinsic lithium ion conductivity of at least10⁻⁵ S/cm.